James Ford

Professor of Medicine (Oncology) and of Genetics and, by courtesy, of Pediatrics

Medicine - Oncology

Bio

Bio

Dr. Ford is a medical oncologist and geneticist at Stanford, devoted to studying the genetic basis of breast and GI cancer development, treatment and prevention. Dr. Ford graduated in 1984 Magna Cum Laude (Biology) from Yale University where he later received his M.D. degree from the School of Medicine in 1989. He was a internal medicine resident (1989-91), Clinical Fellow in Medical Oncology (1991-94), Research Fellow of Biological Sciences (1993-97) at Stanford, and joined the faculty in 1998. He is currently Professor of Medicine (Oncology) and Genetics, and Director of the Stanford Cancer Genetics Clinic and the Cancer Genomics Program at the Stanford University Medical Center.

Dr. Ford’s research goals are to understand the role of genetic changes in cancer genes in the risk and development of common cancers. He studies the role of the p53 and BRCA1 tumor suppressor genes in DNA repair, and uses techniques for high-throughput genomic analyses of cancer to identify molecular signatures for targeted therapies. Dr. Ford’s clinical interests include the diagnosis and treatment of patients with a hereditary pre-disposition to cancer. He runs the Stanford Cancer Genetics Clinic, that sees patients for genetic counseling and testing of hereditary cancer syndromes for prevention and early diagnosis of cancer in high-risk individuals and populations. He has recently been named the Director of Stanford’s new Cancer Genomics Program, performing next-generation tumor profiling to identify novel genetic targets for personalized targeted therapies, and directs the Molecular Tumor Board.

Dr. Ford is an editor of numerous scientific journals, including Cancer Research, DNA Repair, and PLoS Genetics. He has recently been named the founding Editor-in-Chief of JCO Precision Oncology.

Links

Research & Scholarship

Current Research and Scholarly Interests

The major investigative focus of this laboratory and translational research program is to explore the mammalian genetic determinants of the inducible response and cellular sensitivity to DNA damage, focusing particularly on the effects of the p53 and BRCA1 gene products on DNA repair and cancer susceptibility. We have found that loss of p53 and BRCA1 function results in defective repair of DNA damage, including effects on homologous recombination, nucleotide and base-excision repair. In addition, we are exploring ways to exploit the DNA repair deficiency of p53 and BRCA1 mutant cancer cells and to identify targeted therapeutic approaches for the treatment and prevention of related cancers.

Role of BRCA1 in base-excision DNA repair (BER): BRCA1 appears to have complex regulatory effects on multiple DNA repair pathways in addition to their shared role in homologous-recombination and DNA double strand break repair. We first described that breast cancer cell lines mutant for the BRCA1 gene exhibit sensitivity to oxidative DNA damage. We also developed a novel viral based “host-cell reactivation” assay to measure the repair of oxidative DNA damage in living cells using an adenoviral GFP reporter gene, and demonstrated that BRCA1 mutant cells were defective in BER.

Discovery of small molecules that activate BER and may prevent BRCA1-associated tumors: We designed and performed a high-throughput screen to identify small-molecules that enhance DNA repair in a BRCA1 mutant background, and thus may serve as candidate agents for prevention of cancer by enhancing DNA repair and interrupting multistep mutagenesis. Several of these drugs are potentially “repurposeable” and are currently or were previously used in humans for other indications. We have shown activity of two in preventing the development of BRCA1-associated breast cancers in mice and are developing plans for a clinical trial using the lead hit for prevention of BRCA1-associated premalignant changes in ovaries from women undergoing risk-reducing bilateral oopherectomies.

Clinical translation of Next-Generation Sequencing for hereditary cancer risk assessment: We recently led the first clinical study of next-generation gene panel DNA sequencing among women referred for breast cancer risk assessment using germline DNA samples from our large translational research biobank containing more than 2000 specimens, all donated by individuals tested for BRCA1/2 or other gene mutations. We found that >10% of patients had potentially pathogenic mutations in genes other than BRCA1/2, thus doubling the rate of identified germline cancer susceptibility gene alterations in this population, a discovery that has enabled early detection of cancers.

Targeting TNBC and other malignancies with DNA damaging drugs and PARP: We found through preclinical studies and clinical trials that nearly all BRCA mutation associated breast cancer, and approximately half of non-BRCA mutant TNBC exhibit clinical sensitivity to platinum chemotherapy and synthetic lethality with PARP inhibitors. As part of these efforts, we performed extensive correlative studies on tumor tissue and germline DNA samples obtained from patients enrolled in a large, multi-institutional neoadjuvant clinical trial, using gene expression microarrays, DNA copy-number analyses, and germline DNA sequencing. We described a bioinformatic measure of homologous recombination deficiency (HRD) that is highly predictive of clinical response in these patients. Our current and future research goals in this area is to leverage our expertise in germline and tumor genomics to identify patients with breast and other cancers harboring DNA repair gene defects and HRD for treatment using PARP inhibitors and other DNA repair directed therapies (ATR and DNA-PK inhibitors). We have also developed breast cancer cell lines resistant to PARP-inhibitors and are exploring the mechanism for this drug resistance.

Clinical Trials

This research trial studies using genomic profiling to recommend anticancer treatment to
patients with cancer that has spread beyond the original site of the tumor (metastatic
cancer). Genomic profiling studies the deoxyribonucleic acid (DNA) of a tumor to detect
genetic changes or abnormalities. This information can then be used to recommend treatments
that may be more likely to result in a beneficial response. It is not yet known whether
genomic profiling will detect abnormalities that can be used to make treatment
recommendations and whether treatment based on genomic profiling is more effective than
standard treatment.

To investigate bevacizumab in combination with carboplatin and capecitabine for patients with
unresectable or metastatic GEJ or gastric cancers. We hope that by adding bevacizumab to
standard chemotherapy for this patient population we will improve Progression Free Survival
by 80% over historical controls.

Stanford is currently not accepting patients for this trial.For more information, please contact Prachi Nandoskar, (650) 725 - 0438.

This multicenter, randomized, adaptive Phase II/III study will evaluate the efficacy and
safety of trastuzumab emtansine (T-DM1) compared to standard taxane (docetaxel or paclitaxel)
treatment in participants with human epidermal growth factor receptor 2 (HER2)-positive
advanced gastric cancer. At the start of the trial (stage 1), participants will be randomized
with a ratio 2:2:1 to one of three treatment arms: Arm A: trastuzumab emtansine 3.6 milligram
per kilogram (mg/kg) per intravenous injection (IV) every 3 weeks; Arm B: trastuzumab
emtansine 2.4 mg/kg IV every week; Arm C: standard taxane therapy (docetaxel 75 milligram per
meter square [mg/m^2] IV every 3 weeks or paclitaxel 80 mg/m^2 kg IV every week per
investigator choice). At the end of the first stage of the study, the dose and schedule of
trastuzumab emtansine that will be used in the second stage of the study will be selected by
an Independent Data Monitoring Committee (IDMC). The regimen selection analysis will be made
after approximately 100 participants across all three study arms have been treated for at
least 12 weeks.
Once a trastuzumab emtansine regimen has been selected, Stage I participants who were
assigned to the treatment arm which was selected for Stage II of the study and participants
who were in the standard taxane group will continue to receive their assigned treatment
regimen. Stage I participants who were assigned to the regimen that was not selected for
further evaluation will continue to receive their assigned regimen and will continue to be
followed for efficacy and safety. In Stage II of the study, additional participants will be
recruited and randomized with a ratio 2:1 to either the selected regimen of trastuzumab
emtansine or to the standard taxane therapy. Participants will receive study treatment until
disease progression, unacceptable toxicity, initiation of another cancer therapy or
withdrawal.

Stanford is currently not accepting patients for this trial.For more information, please contact Prachi Nandoskar, 650-725-0438.

This phase II trial studies how well treatment that is directed by genetic testing works in
patients with solid tumors or lymphomas that have progressed following at least one line of
standard treatment or for which no agreed upon treatment approach exists. Genetic tests look
at the unique genetic material (genes) of patients' tumor cells. Patients with genetic
abnormalities (such as mutations, amplifications, or translocations) may benefit more from
treatment which targets their tumor's particular genetic abnormality. Identifying these
genetic abnormalities first may help doctors plan better treatment for patients with solid
tumors, lymphomas, or multiple myeloma.

Our research of the biology of upper gastrointestinal cancers involves the study of tissue
samples and cells from biopsies of persons with gastric or esophageal cancer or blood samples
from upper gastrointestinal cancer patients and persons at high inherited risk for these
cancers. We hope to learn the role genes and proteins play in the development of gastric and
esophageal cancer.

The Gastric Cancer Registry will combine data acquired directly from patients with gastric
cancer via an online questionnaire with genomic data obtained from blood and tissue samples.
The purpose of this registry is to gain better understanding of the causes of gastric cancer,
both environmental and genetic; whether certain genomic data can predict outcomes of
treatment and survival; as well as explore the issues that effect the quality of life of
these patients after diagnosis and treatment.

This is a Phase 1/2, multi-center, open-label study designed to evaluate the safety and
efficacy of LOXO-195 when administered orally to patients with NTRK fusion cancers treated
with prior TRK inhibition or non-fusion NTRK altered cancers regardless of prior kinase
inhibitor treatment.

The purpose of this study is to try to understand the biology of development of breast,
ovarian, fallopian tube, peritoneal or endometrial cancer from persons at high genetic risk
for these diseases. The influence of environmental factors on cancer development in
individuals and families will be studied. The efficacy of treatments for these diseases will
be evaluated.

This multicenter, non-randomized, open-label study will evaluate the efficacy and safety of
six treatment regimens in participants with advanced solid tumors for whom therapies that
will convey clinical benefit are not available and/or are not suitable options per the
treating physician's judgment.

Publications

All Publications

Abstract

The development of stereotactic body radiation therapy (SBRT) has revolutionized radiation therapy for lung cancers and is an emerging treatment option for pancreatic cancers. However, there are many questions on how to optimize its use in chemoradiotherapy. The most relevant addition to radiotherapy regimens are inhibitors of DNA repair and DNA damage response pathways. One such class of agents are inhibitors of poly (ADP-ribose) polymerase (PARP). In this study we examined the effects of the PARP inhibitor LT626 in combination with ionizing radiation in lung and pancreatic cancers. Our study demonstrated that combination treatment with LT626 and radiation effectively inhibited growth in lung and pancreatic cancer cell lines, better than individual treatment alone. Combination treatment also increased expression of γH2AX and 53BP1 foci and upregulated expression of phosphorylated ATM, ATR and their respective kinases. Using in vivo lung cancer xenograft models we demonstrated that LT626 functioned as an effective radiosensitizer during fractionated radiation treatment, leading to significant decrease in tumor burden and doubling the median survival compared to control group. Overall our in vitro and in vivo studies showed that PARP inhibitor LT626 acted synergistically with radiation in lung and pancreatic cancers.

Abstract

The advent of genomic diagnostic technologies such as next-generation sequencing has recently enabled the use of genomic information to guide targeted treatment in patients with cancer, an approach known as precision medicine. However, clinical outcomes, including survival and the cost of health care associated with precision cancer medicine, have been challenging to measure and remain largely unreported.We conducted a matched cohort study of 72 patients with metastatic cancer of diverse subtypes in the setting of a large, integrated health care delivery system. We analyzed the outcomes of 36 patients who received genomic testing and targeted therapy (precision cancer medicine) between July 1, 2013, and January 31, 2015, compared with 36 historical control patients who received standard chemotherapy (n = 29) or best supportive care (n = 7).The average progression-free survival was 22.9 weeks for the precision medicine group and 12.0 weeks for the control group (P = .002) with a hazard ratio of 0.47 (95% CI, 0.29 to 0.75) when matching on age, sex, histologic diagnosis, and previous lines of treatment. In a subset analysis of patients who received all care within the Intermountain Healthcare system (n = 44), per patient charges per week were $4,665 in the precision treatment group and $5,000 in the control group (P = .126).These findings suggest that precision cancer medicine may improve survival for patients with refractory cancer without increasing health care costs. Although the results of this study warrant further validation, this precision medicine approach may be a viable option for patients with advanced cancer.

Abstract

This study was designed to assess efficacy, safety, and predictors of response to iniparib in combination with gemcitabine and carboplatin in early-stage triple-negative and BRCA1/2 mutation-associated breast cancer.This single-arm phase II study enrolled patients with stage I to IIIA (T ≥ 1 cm) estrogen receptor-negative (≤ 5%), progesterone receptor-negative (≤ 5%), and human epidermal growth factor receptor 2-negative or BRCA1/2 mutation-associated breast cancer. Neoadjuvant gemcitabine (1,000 mg/m(2) intravenously [IV] on days 1 and 8), carboplatin (area under curve of 2 IV on days 1 and 8), and iniparib (5.6 mg/kg IV on days 1, 4, 8, and 11) were administered every 21 days for four cycles, until the protocol was amended to six cycles. The primary end point was pathologic complete response (no invasive carcinoma in breast or axilla). All patients underwent comprehensive BRCA1/2 genotyping, and homologous recombination deficiency was assessed by loss of heterozygosity (HRD-LOH) in pretreatment core breast biopsies.Among 80 patients, median age was 48 years; 19 patients (24%) had germline BRCA1 or BRCA2 mutations; clinical stage was I (13%), IIA (36%), IIB (36%), and IIIA (15%). Overall pathologic complete response rate in the intent-to-treat population (n = 80) was 36% (90% CI, 27 to 46). Mean HRD-LOH scores were higher in responders compared with nonresponders (P = .02) and remained significant when BRCA1/2 germline mutations carriers were excluded (P = .021).Preoperative combination of gemcitabine, carboplatin, and iniparib is active in the treatment of early-stage triple-negative and BRCA1/2 mutation-associated breast cancer. The HRD-LOH assay was able to identify patients with sporadic triple-negative breast cancer lacking a BRCA1/2 mutation, but with an elevated HRD-LOH score, who achieved a favorable pathologic response. Confirmatory controlled trials are warranted.

Abstract

Germline CDH1 mutations confer a high lifetime risk of developing diffuse gastric (DGC) and lobular breast cancer (LBC). A multidisciplinary workshop was organised to discuss genetic testing, surgery, surveillance strategies, pathology reporting and the patient's perspective on multiple aspects, including diet post gastrectomy. The updated guidelines include revised CDH1 testing criteria (taking into account first-degree and second-degree relatives): (1) families with two or more patients with gastric cancer at any age, one confirmed DGC; (2) individuals with DGC before the age of 40 and (3) families with diagnoses of both DGC and LBC (one diagnosis before the age of 50). Additionally, CDH1 testing could be considered in patients with bilateral or familial LBC before the age of 50, patients with DGC and cleft lip/palate, and those with precursor lesions for signet ring cell carcinoma. Given the high mortality associated with invasive disease, prophylactic total gastrectomy at a centre of expertise is advised for individuals with pathogenic CDH1 mutations. Breast cancer surveillance with annual breast MRI starting at age 30 for women with a CDH1 mutation is recommended. Standardised endoscopic surveillance in experienced centres is recommended for those opting not to have gastrectomy at the current time, those with CDH1 variants of uncertain significance and those that fulfil hereditary DGC criteria without germline CDH1 mutations. Expert histopathological confirmation of (early) signet ring cell carcinoma is recommended. The impact of gastrectomy and mastectomy should not be underestimated; these can have severe consequences on a psychological, physiological and metabolic level. Nutritional problems should be carefully monitored.

Abstract

Triple-negative breast cancers (TNBCs) are characterised by a wide spectrum of genomic alterations, some of which might be caused by defects in DNA repair processes such as homologous recombination (HR). Despite this understanding, associating particular patterns of genomic instability with response to therapy has been challenging. Here, we show that Allelic-imbalanced Copy Number Aberrations (AiCNA) are more prevalent in TNBCs that respond to platinum-based chemotherapy, thus providing a candidate predictive biomarker for this disease. Furthermore, we show that a high level of AiCNA is linked with elevated expression of a meiosis-associated gene HORMAD1. Elevated HORMAD1 expression suppresses RAD51-dependent HR and drives the use of alternative forms of DNA repair, the generation of AiCNAs as well as sensitising cancer cells to HR targeting therapies. Our data therefore provides a mechanistic association between HORMAD1 expression, a specific pattern of genomic instability and an association with response to platinum-based chemotherapy in TNBC.

Abstract

Multiple-gene sequencing is entering practice, but its clinical value is unknown. We evaluated the performance of a customized germline-DNA sequencing panel for cancer-risk assessment in a representative clinical sample.Patients referred for clinical BRCA1/2 testing from 2002 to 2012 were invited to donate a research blood sample. Samples were frozen at -80° C, and DNA was extracted from them after 1 to 10 years. The entire coding region, exon-intron boundaries, and all known pathogenic variants in other regions were sequenced for 42 genes that had cancer risk associations. Potentially actionable results were disclosed to participants.In total, 198 women participated in the study: 174 had breast cancer and 57 carried germline BRCA1/2 mutations. BRCA1/2 analysis was fully concordant with prior testing. Sixteen pathogenic variants were identified in ATM, BLM, CDH1, CDKN2A, MUTYH, MLH1, NBN, PRSS1, and SLX4 among 141 women without BRCA1/2 mutations. Fourteen participants carried 15 pathogenic variants, warranting a possible change in care; they were invited for targeted screening recommendations, enabling early detection and removal of a tubular adenoma by colonoscopy. Participants carried an average of 2.1 variants of uncertain significance among 42 genes.Among women testing negative for BRCA1/2 mutations, multiple-gene sequencing identified 16 potentially pathogenic mutations in other genes (11.4%; 95% CI, 7.0% to 17.7%), of which 15 (10.6%; 95% CI, 6.5% to 16.9%) prompted consideration of a change in care, enabling early detection of a precancerous colon polyp. Additional studies are required to quantify the penetrance of identified mutations and determine clinical utility. However, these results suggest that multiple-gene sequencing may benefit appropriately selected patients.

Abstract

Whole-genome sequencing (WGS) is increasingly applied in clinical medicine and is expected to uncover clinically significant findings regardless of sequencing indication.To examine coverage and concordance of clinically relevant genetic variation provided by WGS technologies; to quantitate inherited disease risk and pharmacogenomic findings in WGS data and resources required for their discovery and interpretation; and to evaluate clinical action prompted by WGS findings.An exploratory study of 12 adult participants recruited at Stanford University Medical Center who underwent WGS between November 2011 and March 2012. A multidisciplinary team reviewed all potentially reportable genetic findings. Five physicians proposed initial clinical follow-up based on the genetic findings.Genome coverage and sequencing platform concordance in different categories of genetic disease risk, person-hours spent curating candidate disease-risk variants, interpretation agreement between trained curators and disease genetics databases, burden of inherited disease risk and pharmacogenomic findings, and burden and interrater agreement of proposed clinical follow-up.Depending on sequencing platform, 10% to 19% of inherited disease genes were not covered to accepted standards for single nucleotide variant discovery. Genotype concordance was high for previously described single nucleotide genetic variants (99%-100%) but low for small insertion/deletion variants (53%-59%). Curation of 90 to 127 genetic variants in each participant required a median of 54 minutes (range, 5-223 minutes) per genetic variant, resulted in moderate classification agreement between professionals (Gross κ, 0.52; 95% CI, 0.40-0.64), and reclassified 69% of genetic variants cataloged as disease causing in mutation databases to variants of uncertain or lesser significance. Two to 6 personal disease-risk findings were discovered in each participant, including 1 frameshift deletion in the BRCA1 gene implicated in hereditary breast and ovarian cancer. Physician review of sequencing findings prompted consideration of a median of 1 to 3 initial diagnostic tests and referrals per participant, with fair interrater agreement about the suitability of WGS findings for clinical follow-up (Fleiss κ, 0.24; P

Abstract

Some colorectal cancers (CRC) display microsatellite instability (MSI) leading to mutations in genes such as MRE11. The aim of this study was to determine whether MSI or MRE11 mutational status correlates with sensitivity to the PARP inhibitor LT-626 and whether LT-626 synergizes with DNA-damaging chemotherapeutic agents. CRC cells harboring biallelic MRE11 mutations were more sensitive to LT-626 and stable overexpression or knock-down of MRE11 in cell lines correlated with sensitivity. Synergism was evident between LT-626 and cisplatin, oxaliplatin and SN-38 suggesting that PARP inhibitors in combination with DNA damaging agents may be a successful strategy for treatment of CRC.

Abstract

Gastric cancer is the second-leading cause of global cancer deaths, with metastatic disease representing the primary cause of mortality. To identify candidate drivers involved in oncogenesis and tumor evolution, we conduct an extensive genome sequencing analysis of metastatic progression in a diffuse gastric cancer. This involves a comparison between a primary tumor from a hereditary diffuse gastric cancer syndrome proband and its recurrence as an ovarian metastasis.Both the primary tumor and ovarian metastasis have common biallelic loss-of-function of both the CDH1 and TP53 tumor suppressors, indicating a common genetic origin. While the primary tumor exhibits amplification of the Fibroblast growth factor receptor 2 (FGFR2) gene, the metastasis notably lacks FGFR2 amplification but rather possesses unique biallelic alterations of Transforming growth factor-beta receptor 2 (TGFBR2), indicating the divergent in vivo evolution of a TGFBR2-mutant metastatic clonal population in this patient. As TGFBR2 mutations have not previously been functionally validated in gastric cancer, we modeled the metastatic potential of TGFBR2 loss in a murine three-dimensional primary gastric organoid culture. The Tgfbr2 shRNA knockdown within Cdh1-/-; Tp53-/- organoids generates invasion in vitro and robust metastatic tumorigenicity in vivo, confirming Tgfbr2 metastasis suppressor activity.We document the metastatic differentiation and genetic heterogeneity of diffuse gastric cancer and reveal the potential metastatic role of TGFBR2 loss-of-function. In support of this study, we apply a murine primary organoid culture method capable of recapitulating in vivo metastatic gastric cancer. Overall, we describe an integrated approach to identify and functionally validate putative cancer drivers involved in metastasis.

Abstract

Gastric cancer is a global public health concern, ranking as the fourth leading cause of cancer mortality, with a 5-year survival of only 20%. Approximately 10% of gastric cancers appear to have a familial predisposition, and about half of these can be attributed to hereditary germline mutations. We review the genetic syndromes and current standards for genetic counseling, testing, and medical management for screening and treatment of gastric cancer. Recently, germline mutations in the E-cadherin/CDH1 gene have been identified in families with an autosomal dominant inherited predisposition to gastric cancer of the diffuse type. The cumulative lifetime risk of developing gastric cancer in CDH1 mutation carriers is up to 80%, and women from these families also have an increased risk for developing lobular breast cancer. Prophylactic gastrectomies are recommended in unaffected CDH1 mutation carriers, because screening endoscopic examinations and blind biopsies have proven inadequate for surveillance. In addition to this syndrome, gastric cancer risk is elevated in Lynch syndrome associated with germline mutations in DNA mismatch repair genes and microsatellite instability, in hereditary breast and ovarian cancer syndrome due to germline BRCA1 and BRCA2 mutations, in familial adenomatous polyposis caused by germline APC mutations, in Li-Fraumeni syndrome due to germline p53 mutations, in Peutz-Jeghers syndrome associated with germline STK11 mutations, and in juvenile polyposis syndrome associated with germline mutations in the SMAD4 and BMPR1A genes. Guidelines for genetic testing, counseling, and management of individuals with hereditary diffuse gastric cancer are suggested. A raised awareness among the physician and genetic counseling communities regarding these syndromes may allow for increased detection and prevention of gastric cancers in these high-risk individuals.

Abstract

The basal-like subtype of breast cancers, including those that contain germline mutations in BRCA1, tend to be triple-negative (i.e. lack expression of estrogen and progesterone receptors and lack overexpression/amplification of the HER2/neu oncogene), which renders them relatively insensitive to existing "targeted" therapy. BRCA1-mutated and basal-like breast cancers harbor compromised ability for repairing oxidative DNA damage by the DNA base-excision repair pathway. We found that this defective repair mechanism predicts sensitivity to elesclomol, an experimental therapeutic that produces elevated levels of oxidative DNA damage. In conclusion, BRCA1-mutated and/or basal-like breast cancers may benefit from treatment regimens that include elesclomol.

Is breast cancer a part of Lynch syndrome?Breast cancer research : BCR2012; 14 (4): 110

Abstract

ABSTRACT: A long-standing question is whether breast cancer is an integral part of Lynch syndrome, also known as hereditary non-polyposis colorectal cancer. A recent study by Lotsari and colleagues analyzes molecular features of breast cancers from families with Lynch syndrome, including germline mutation carriers and their non-mutation carrier siblings, and controls with sporadic breast cancer. The study finds microsatellite instability and loss of mismatch DNA repair protein expression in one third and two thirds of Lynch syndrome samples, respectively, but in none of the non-mutation carriers or controls. Overall, the age of diagnosis of breast cancer in Lynch syndrome mutation carriers is no different than that in non-carriers, but diagnosis age was lower in those carriers whose breast tumors exhibited defects in mismatch repair. These results have important implications for genetic counseling and genetic testing of families with breast cancer and other tumors associated with Lynch syndrome, such as colorectal and endometrial cancers.

Abstract

Testing has been advocated for all persons with newly diagnosed colorectal cancer to identify families with the Lynch syndrome, an autosomal dominant cancer-predisposition syndrome that is a paradigm for personalized medicine.To estimate the effectiveness and cost-effectiveness of strategies to identify the Lynch syndrome, with attention to sex, age at screening, and differential effects for probands and relatives.Markov model that incorporated risk for colorectal, endometrial, and ovarian cancers.Published literature.All persons with newly diagnosed colorectal cancer and their relatives.Lifetime.Third-party payer.Strategies based on clinical criteria, prediction algorithms, tumor testing, or up-front germline mutation testing, followed by tailored screening and risk-reducing surgery.Life-years, cancer cases and deaths, costs, and incremental cost-effectiveness ratios.The benefit of all strategies accrued primarily to relatives with a mutation associated with the Lynch syndrome, particularly women, whose life expectancy could increase by approximately 4 years with hysterectomy and salpingo-oophorectomy and adherence to colorectal cancer screening recommendations. At current rates of germline testing, screening, and prophylactic surgery, the strategies reduced deaths from colorectal cancer by 7% to 42% and deaths from endometrial and ovarian cancer by 1% to 6%. Among tumor-testing strategies, immunohistochemistry followed by BRAF mutation testing was preferred, with an incremental cost-effectiveness ratio of $36,200 per life-year gained.The number of relatives tested per proband was a critical determinant of both effectiveness and cost-effectiveness, with testing of 3 to 4 relatives required for most strategies to meet a threshold of $50,000 per life-year gained. Immunohistochemistry followed by BRAF mutation testing was preferred in 59% of iterations in probabilistic sensitivity analysis at a threshold of $100,000 per life-year gained. Screening for the Lynch syndrome with immunohistochemistry followed by BRAF mutation testing only up to age 70 years cost $44,000 per incremental life-year gained compared with screening only up to age 60 years, and screening without an upper age limit cost $88,700 per incremental life-year gained compared with screening only up to age 70 years.Other types of cancer, uncertain family pedigrees, and genetic variants of unknown significance were not considered.Widespread colorectal tumor testing to identify families with the Lynch syndrome could yield substantial benefits at acceptable costs, particularly for women with a mutation associated with the Lynch syndrome who begin regular screening and have risk-reducing surgery. The cost-effectiveness of such testing depends on the participation rate among relatives at risk for the Lynch syndrome.National Institutes of Health.

Abstract

Breast cancers due to germline mutations or altered expression of the BRCA1 gene associate with an aggressive clinical course and frequently exhibit a "triple-negative" phenotype, i.e. lack of expression of the estrogen and progesterone hormone receptors and lack of overexpression of the HER2/NEU oncogene, thereby rendering them relatively insensitive to hormonal manipulation and targeted HER2 therapy, respectively. BRCA1 plays a role in multiple DNA repair pathways, and thus, when mutated, results in sensitivity to certain DNA damaging drugs.Here, we used a Brca1 murine mammary epithelial cell (MMEC) model to examine the effect of loss of Brca1 on cellular sensitivity to various chemotherapy drugs. To explore novel therapeutic strategies, we included DNA damaging and non-DNA damaging drugs whose mechanisms are dependent and independent of DNA repair, respectively, and drugs that are used in standard and non-standard lines of therapy for breast cancer. To understand the cellular mechanism, we also determined the role that DNA repair plays in sensitivity to these drugs. We found that cisplatin and gemcitabine had the greatest specific therapeutic benefit to Brca1-deficient MMECs, and that when used in combination produced a synergistic effect. This sensitivity may be attributed in part to defective NER, which is one of the DNA repair pathways normally responsible for repairing DNA adducts produced by cisplatin and is shown in this study to be defective in Brca1-deficient MMECs. Brca1-deficient MMECs were not differentially sensitive to the standard breast cancer chemotherapy drugs doxorubicin, docetaxel or 5-FU.Both cisplatin and gemcitabine should be explored in clinical trials for first line regimens for BRCA1-associated and triple-negative breast cancer.

Abstract

Contralateral second primary breast cancers occur in 4% of female breast cancer survivors. Little is known about differences in risk for second primary breast cancers related to the estrogen and progesterone receptor (hormone receptor [HR]) status of the first tumor.We calculated standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) for contralateral primary breast cancers among 4927 women diagnosed with a first breast cancer between January 1, 1992, and December 31, 2004, using the National Cancer Institute's Surveillance, Epidemiology, and End Results database.For women whose first breast tumors were HR positive, risk of contralateral primary breast cancer was elevated, compared with the general population, adjusted for age, race, and calendar year (SIR = 2.22, 95% CI = 2.15 to 2.29, absolute risk [AR] = 13 cases per 10 000 person-years [PY]), and was not related to the HR status of the second tumor. For women whose first breast tumors were HR negative, the risk of a contralateral primary tumor was statistically significantly higher than that for women whose first tumors were HR positive (SIR = 3.57, 95% CI = 3.38 to 3.78, AR = 18 per 10 000 PY), and it was associated with a much greater likelihood of an HR-negative second tumor (SIR for HR-positive second tumors = 1.94, 95% CI = 1.77 to 2.13, AR = 20 per 10 000 PY; SIR for HR-negative second tumors = 9.81, 95% CI = 9.00 to 10.7, AR = 24 per 10 000 PY). Women who were initially diagnosed with HR-negative tumors when younger than 30 years had greatly elevated risk of HR-negative contralateral tumors, compared with the general population (SIR = 169, 95% CI = 106 to 256, AR = 77 per 10 000 PY). Incidence rates for any contralateral primary cancer following an HR-negative or HR-positive tumor were higher in non-Hispanic blacks, Hispanics, and Asians or Pacific Islanders than in non-Hispanic whites.Risk for contralateral second primary breast cancers varies substantially by HR status of the first tumor, age, and race and/or ethnicity. Women with HR-negative first tumors have nearly a 10-fold elevated risk of developing HR-negative second tumors, compared with the general population. These findings warrant intensive surveillance for second breast cancers in women with HR-negative tumors.

Abstract

Subtypes of breast cancer that represent the two major types of epithelial cells in the breast (luminal and basal) carry distinct histopathologic profiles. Breast cancers of the basal-like subtype, which include the majority of hereditary breast cancers due to mutations in the breast cancer susceptibility gene 1 (BRCA1), frequently assume triple-negative status, i.e., they lack expression of estrogen receptor-alpha and progesterone receptor, and lack overexpression or amplification of the HER2/NEU oncogene. Defects in DNA damage response pathways result in genome instability and lead to carcinogenesis, but may also be exploited for therapeutic purposes. We analyzed repair of oxidative DNA damage by the base-excision repair (BER) pathway, which when aberrant leads to genomic instability and breast carcinogenesis, in cell lines that represent the different subtypes of breast cancer and in the presence of BRCA1 deficiency. We found that basal-like and BRCA1-mutated breast cancer cells were defective in BER of oxidative DNA damage, and that this defect conferred sensitivity to inhibition of poly(ADP-ribose) polymerase, a DNA repair enzyme. The defect may be attributed, at least in part, to a novel role for BRCA1 in the BER pathway. Overall, these data offer preventive, prognostic, and therapeutic usefulness.

Abstract

There are established differences in breast cancer epidemiology between Asian and white individuals, but little is known about hereditary breast cancer in Asian populations. Although increasing numbers of Asian individuals are clinically tested for BRCA1/2 mutations, it is not known whether computer models that predict mutations work accurately in Asian individuals. We compared the performance in Asian and white individuals of two widely used BRCA1/2 mutation prediction models, BRCAPRO and Myriad II.We evaluated BRCAPRO and Myriad II in 200 Asian individuals and a matched control group of 200 white individuals who were tested for BRCA1/2 mutations at four cancer genetics clinics, by comparing numbers of observed versus predicted mutation carriers and by evaluating area under the receiver operating characteristic curve (AUC) for each model.BRCAPRO and Myriad II accurately predicted the number of white BRCA1/2 mutation carriers (25 observed v 24 predicted by BRCAPRO; 25 predicted by Myriad II, P > or = .69), but underpredicted Asian carriers by two-fold (49 observed v 25 predicted by BRCAPRO; 26 predicted by Myriad II; P < or = 3 x 10(-7)). For BRCAPRO, this racial difference reflects substantial underprediction of Asian BRCA2 mutation carriers (26 observed v 4 predicted; P = 1 x 10(-30)); for Myriad II, separate mutation predictions were not available. For both models, AUCs were nonsignificantly lower in Asian than white individuals, suggesting less accurate discrimination between Asian carriers and noncarriers.Both BRCAPRO and Myriad II underestimated the proportion of BRCA1/2 mutation carriers, and discriminated carriers from noncarriers less well, in Asian compared with white individuals.

Abstract

Approximately 10% of patients with gastric cancer show familial clustering, and 3% show autosomal dominance and high penetrance. Hereditary diffuse gastric cancer (HDGC) is an autosomal-dominant, inherited cancer syndrome in which affected individuals develop diffuse-type gastric cancer at a young age. Inactivating mutations in the E-cadherin gene CDH1 have been identified in 30% to 50% of patients. CDH1 mutation carriers have an approximately 70% lifetime risk of developing DGC, and affected women carry an additional 20% to 40% risk of developing lobular breast cancer. Because endoscopic surveillance is ineffective in identifying early HDGC, gene-directed prophylactic total gastrectomy currently is offered for CDH1 mutation carriers. In series of asymptomatic individuals undergoing total gastrectomy for CDH1 mutations, the removed stomachs usually contain small foci of early DGC, making surgery not prophylactic but curative. The authors of this review recommend consideration of total gastrectomy in CDH1 mutation carriers at an age 5 years younger than the youngest family member who developed gastric cancer. Individuals who choose not to undergo prophylactic gastrectomy should be followed with biannual chromoendoscopy, and women with CDH1 mutations also should undergo regular surveillance with magnetic resonance imaging studies of the breast. Because of the emergence of gene-directed gastrectomy for HDGC, today, a previously lethal disease is detected by molecular techniques, allowing curative surgery at an early stage.

Abstract

Approximately 1% to 3% of all gastric cancers are associated with families exhibiting an autosomal dominant pattern of susceptibility. E-cadherin (CDH1) truncating mutations have been shown to be present in approximately 30% of families with hereditary diffuse gastric cancer (HDGC) and are associated with a significantly increased risk of gastric cancer and lobular breast cancer.Individuals from a large kindred with HDGC who were identified to have a CDH1 mutation prospectively underwent comprehensive screening with stool occult blood testing, standard upper gastrointestinal endoscopy with random gastric biopsies, high-magnification endoscopy with random gastric biopsies, endoscopic ultrasonography, CT, and PET scans to evaluate the stomach for occult cancer. Subsequently, they each underwent total gastrectomy with D-2 node dissection and Roux-en-Y esophagojejunostomy. The stomach and resected lymph nodes were evaluated pathologically.Six patients were identified as CDH1 carriers from a single family. There were 2 men and 4 women. The mean age was 54 years (range, 51-57 years). No patient had any signs or symptoms of gastric cancer. Exhaustive preoperative stomach evaluation was normal in each case, and the stomach and adjacent lymph nodes appeared normal at surgery. However, each patient (6 of 6, 100%) was found to have multiple foci of T1 invasive diffuse gastric adenocarcinoma (pure signet-ring cell type). No patient had lymph node or distant metastases. Each was staged as T1N0M0. Each patient recovered uneventfully without morbidity or mortality.CDH1 mutations in individuals from families with HDGC are associated with gastric cancer in a highly penetrant fashion. CDH1 mutations are an indication for total gastrectomy in these patients. This mutation will identify patients with cancer before other detectable symptoms or signs of the disease.

Abstract

Genomic instability is a major feature of neoplastic development in colorectal carcinoma and other cancers. Specific genomic instability events, such as deletions in chromosomes and other alterations in gene copy number, have potential utility as biologically relevant prognostic biomarkers. For example, genomic deletions on chromosome arm 18q are an indicator of colorectal carcinoma behavior and potentially useful as a prognostic indicator. Adapting a novel genomic technology called molecular inversion probes which can determine gene copy alterations, such as genomic deletions, we designed a set of probes to interrogate several hundred individual exons of >200 cancer genes with an overall distribution covering all chromosome arms. In addition, >100 probes were designed in close proximity of microsatellite markers on chromosome arm 18q. We analyzed a set of colorectal carcinoma cell lines and primary colorectal tumor samples for gene copy alterations and deletion mutations in exons. Based on clustering analysis, we distinguished the different categories of genomic instability among the colorectal cancer cell lines. Our analysis of primary tumors uncovered several distinct categories of colorectal carcinoma, each with specific patterns of 18q deletions and deletion mutations in specific genes. This finding has potential clinical ramifications given the application of 18q loss of heterozygosity events as a potential indicator for adjuvant treatment in stage II colorectal carcinoma.

Abstract

An essential component of the ATR (ataxia telangiectasia-mutated and Rad3-related)-activating structure is single-stranded DNA. It has been suggested that nucleotide excision repair (NER) can lead to activation of ATR by generating such a signal, and in yeast, DNA damage processing through the NER pathway is necessary for checkpoint activation during G1. We show here that ultraviolet (UV) radiation-induced ATR signaling is compromised in XPA-deficient human cells during S phase, as shown by defects in ATRIP (ATR-interacting protein) translocation to sites of UV damage, UV-induced phosphorylation of Chk1 and UV-induced replication protein A phosphorylation and chromatin binding. However, ATR signaling was not compromised in XPC-, CSB-, XPF- and XPG-deficient cells. These results indicate that damage processing is not necessary for ATR-mediated S-phase checkpoint activation and that the lesion recognition function of XPA may be sufficient. In contrast, XP-V cells deficient in the UV bypass polymerase eta exhibited enhanced ATR signaling. Taken together, these results suggest that lesion bypass and not lesion repair may raise the level of UV damage that can be tolerated before checkpoint activation, and that XPA plays a critical role in this activation.

Abstract

The initial step in mammalian nucleotide excision repair (NER) of the major UV-induced photoproducts, cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs), requires lesion recognition. It is believed that the heterodimeric proteins XPC/hHR23B and UV-DDB (UV-damaged DNA binding factor, composed of the p48 and p127 subunits) perform this function in genomic DNA, but their requirement and lesion specificity in vivo remains unknown. Using repair-deficient xeroderma pigmentosum (XP)-A cells that stably express photoproduct-specific photolyases, we determined the binding characteristics of p48 and XPC to either CPDs or 6-4PPs in vivo. p48 localized to UV-irradiated sites that contained either CPDs or 6-4PPs. However, XPC localized only to UV-irradiated sites that contained 6-4PPs, suggesting that XPC does not efficiently recognize CPDs in vivo. XPC did localize to CPDs when p48 was overexpressed in the same cell, signifying that p48 activates the recruitment of XPC to CPDs and may be the initial recognition factor in the NER pathway.

Abstract

In response to a variety of types of DNA damage, the p53 tumor suppressor gene product is activated and regulates a number of downstream cellular processes such as cell cycle arrest, apoptosis and DNA repair. Recent discoveries concerning the regulation of DNA repair processes by p53, such as nucleotide excision repair (NER) and base excision repair (BER) have paved the way for studies to understand the mechanisms governing p53-dependent DNA repair. Although several theories have been proposed, accumulating evidence points to a transcriptional regulatory role for p53 in NER, mediating expression of the global genomic repair (GGR)-specific damage recognition genes, DDB2 and XPC. In BER, a more direct role for p53 has been proposed, potentially acting through protein-protein interactions with BER specific factors. These advances have greatly enhanced our understanding of the role of p53 in DNA repair and this review comprehensively summarizes current opinions on the mechanisms of p53-dependent DNA repair.

Abstract

The tumor suppressor protein p53 functions in many cellular responses to UV-induced DNA damage, including activating the global nucleotide excision repair (NER) pathway. A potential mechanism for the effect on NER is through the ability of p53 to transcriptionally regulate genes that are directly involved in NER. DDB2 is one such gene that is regulated by p53 at both the basal and UV inducible levels. In order to further understand p53's role in NER, we transfected and selected clones that stably overexpress DDB2 in a human p53 deficient cell line. Global genomic repair (GGR) of cyclobutane pyrimidine dimers was significantly increased in the DDB2 expressing cells in comparison to controls, demonstrating that p53 wt protein itself is not directly required for efficient GGR. The protein product of DDB2, p48, is also post-translationally regulated by proteasomal degradation in response to UV irradiation. The regulation of p48 at both the transcriptional level by p53, and post-translationally by the proteasome suggests that p48 may be a rate limiting component of NER.

Abstract

The p53 tumor suppressor gene is an important mediator of the cellular response to ultraviolet (UV)-irradiation-induced DNA damage and affects the efficiency of the nucleotide excision repair (NER) pathway. The mechanism by which p53 regulates NER may be through its ability to act as a transcription factor, and/or through direct interactions with damaged DNA or the repair machinery. p53 has been shown to regulate the expression of the DDB2 gene (encoding the p48 protein) and the XPC gene, two important components of the NER pathway involved in DNA damage recognition. In this study, a localized UV-irradiation technique was used to examine the localization of p53, p48 and XPC proteins in relation to sites of UV photoproducts, in vivo. We did not observe any specific co-localization of p53 with sites of UV-induced DNA damage, but did observe rapid co-localization of both p48 and XPC to these sites. p48 bound to UV photoproducts in cells mutant or deficient for either p53, XPC or XPA, and p48 enhanced XPC binding to lesions, suggesting that p48 is a very early recognition factor of DNA damage. We propose that p53 functions to transcriptionally regulate the DDB2 and XPC NER genes, but does not activate the NER pathway through direct interactions with UV-induced damaged DNA or other repair factors.

p53 and DNA damage-inducible expression of the xeroderma pigmentosum group C genePROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICAAdimoolam, S., Ford, J. M.2002; 99 (20): 12985-12990

Abstract

The p53 tumor suppressor gene product is a transcription factor involved in cell-cycle regulation, apoptosis, and DNA repair. We and others have shown that p53 is required for efficient nucleotide excision repair (NER) of UV-induced DNA lesions. p53-deficient cells are defective in the repair of UV photoproducts in genomic DNA but proficient for transcription-coupled repair. Therefore, we examined whether p53 regulates the expression of genes required for global genomic repair. In this study, we demonstrate that the mRNA and protein products of the xeroderma pigmentosum group C (XPC) gene are UV-inducible in a time- and dose-dependent manner in human WI38 fibroblasts and HCT116 colorectal cancer cells wild type for p53. However, no significant induction of XPC was observed in p53-deficient counterparts to these cells. Furthermore, regulated expression of wild-type p53 in p53 null Li-Fraumeni syndrome human fibroblasts significantly augmented the expression of XPC protein. Analysis of the human XPC gene sequence revealed a putative p53 response element in the XPC promoter that was capable of mediating sequence-specific DNA binding to p53 in vitro. These results provide strong evidence that the NER gene XPC is a DNA damage-inducible and p53-regulated gene and likely plays a role in the p53-dependent NER pathway.

Abstract

Inheritance of a mutation in the gene BRCA1 confers on women a 50-85% lifetime risk of developing breast cancer. Mutations in the TP53 tumor-suppressor gene are found in 70-80% of BRCA1-mutated breast cancer but only 30% of those with wildtype BRCA1 (ref. 3). The p53 protein regulates nucleotide excision repair (NER) through transcriptional regulation of genes involved in the recognition of adducts in genomic DNA. Loss of p53 function results in deficient global genomic repair (GGR), a subset of NER that targets and removes lesions from the whole genome. Here we show that BRCA1 specifically enhances the GGR pathway, independent of p53, and can induce p53-independent expression of the NER genes XPC, DDB2, and GADD45. Defects in the NER pathway in BRCA1-associated breast cancers may be causal in tumor development, suggesting a multistep model of carcinogenesis.

Abstract

UV-damaged DNA-binding activity (UV-DDB) is deficient in some xeroderma pigmentosum group E individuals due to mutation of the p48 gene, but its role in DNA repair has been obscure. We found that UV-DDB is also deficient in cell lines and primary tissues from rodents. Transfection of p48 conferred UV-DDB to hamster cells, and enhanced removal of cyclobutane pyrimidine dimers (CPDs) from genomic DNA and from the nontranscribed strand of an expressed gene. Expression of p48 suppressed UV-induced mutations arising from the nontranscribed strand, but had no effect on cellular UV sensitivity. These results define the role of p48 in DNA repair, demonstrate the importance of CPDs in mutagenesis, and suggest how rodent models can be improved to better reflect cancer susceptibility in humans.

Expression of the p48 xeroderma pigmentosum gene is p53-dependent and is involved in global genomic repairPROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICAHwang, B. J., Ford, J. M., Hanawalt, P. C., Chu, G.1999; 96 (2): 424-428

Abstract

In human cells, efficient global genomic repair of DNA damage induced by ultraviolet radiation requires the p53 tumor suppressor, but the mechanism has been unclear. The p48 gene is required for expression of an ultraviolet radiation-damaged DNA binding activity and is disrupted by mutations in the subset of xeroderma pigmentosum group E cells that lack this activity. Here, we show that p48 mRNA levels strongly depend on basal p53 expression and increase further after DNA damage in a p53-dependent manner. Furthermore, like p53(-/-) cells, xeroderma pigmentosum group E cells are deficient in global genomic repair. These results identify p48 as the link between p53 and the nucleotide excision repair apparatus.

Abstract

We have shown previously that Li-Fraumeni syndrome fibroblasts homozygous for p53 mutations are deficient in the removal of UV-induced cyclobutane pyrimidine dimers from genomic DNA, but still proficient in the transcription-coupled repair pathway (Ford, J. M., and Hanawalt, P. C. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 8876-8880). We have now utilized monoclonal antibodies specific for cyclobutane pyrimidine dimers or 6-4 photoproducts, respectively, to measure their repair in UV-irradiated human fibroblasts. Cells homozygous for p53 mutations were deficient in the repair of both photoproducts, whereas cells heterozygous for mutant p53 exhibited normal repair of 6-4 photoproducts, but decreased initial rates of removal of cyclobutane pyrimidine dimers, compared with normal cells. The specificity of the effect of wild-type p53 on nucleotide excision repair was demonstrated in a p53 homozygous mutant cell line containing a tetracycline-regulated wild-type p53 gene. Wild-type p53 expression and activity were suppressed in the presence of tetracycline, whereas withdrawal of tetracycline resulted in the induction of p53 expression, cell cycle checkpoint activation, and DNA damage-induced apoptosis. The regulated expression of wild-type p53 resulted in the recovery of normal levels of repair of both cyclobutane pyrimidine dimers and 6-4 photoproducts in genomic DNA, but did not alter the transcription-coupled repair of cyclobutane pyrimidine dimers. Therefore, the wild-type p53 gene product is an important determinant of nucleotide excision repair activity in human cells.

LI-FRAUMENI SYNDROME FIBROBLASTS HOMOZYGOUS FOR P53 MUTATIONS ARE DEFICIENT IN GLOBAL DNA-REPAIR BUT EXHIBIT NORMAL TRANSCRIPTION-COUPLED REPAIR AND ENHANCED UV RESISTANCEPROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICAFord, J. M., Hanawalt, P. C.1995; 92 (19): 8876-8880

Abstract

We investigated whether mutations in the p53 tumor suppressor gene alter UV sensitivity and/or repair of UV-induced DNA damage in primary human skin fibroblasts from patients with Li-Fraumeni syndrome, heterozygous for mutations in one allele of the p53 gene (p53 wt/mut) and sublines expressing only mutant p53 (p53 mut). The p53 mut cells were more resistant than the p53 wt/mut cells to UV cytotoxicity and exhibited less UV-induced apoptosis. DNA repair analysis revealed reduced removal of cyclobutane pyrimidine dimers from overall genomic DNA in vivo in p53 mut cells compared with p53 wt/mut or normal cells. However, p53 mut cells retained the ability to preferentially repair damage in the transcribed strands of expressed genes (transcription-coupled repair). These results suggest that loss of p53 function may lead to greater genomic instability by reducing the efficiency of DNA repair but that cellular resistance to DNA-damaging agents may be enhanced through elimination of apoptosis.

Abstract

Gastric cancer ranks as the third leading cause of cancer mortality worldwide and confers a 5-year survival of 20%. While most gastric cancers are sporadic, ~1%-3% can be attributed to inherited cancer predisposition syndromes. Germline E-cadherin/CDH1 mutations have been identified in families with an autosomal dominant inherited predisposition to diffuse gastric cancer. The cumulative risk of gastric cancer for CDH1 mutation carriers by age 80 years is reportedly 70% for men and 56% for women. Female mutation carriers also have an estimated 42% risk for developing lobular breast cancer by age 80 years. However, most individuals meeting clinical criteria for hereditary diffuse gastric cancer syndrome (HDGC) do not have a germline CDH1 mutation, and germline CDH1 mutation carriers do not all exhibit similar clinical outcomes in terms of age of diagnosis or cancer types. E-cadherin (CDH1) as the one known causative gene for HDGC accounts for only 40% of cases, leaving 60% with an unknown genetic diagnosis. In addition to HDGC, we will review other genetic syndromes with elevated gastric cancer risk, as well as newly implicated alterations in other genes (CTNNA1, DOT1L, FBXO24, PRSS1, MAP3K6, MSR1, and INSR) that may affect gastric cancer susceptibility and age-specific penetrance.

Abstract

The enzyme MTH1 cleanses the cellular nucleotide pool of oxidatively damaged 8-oxo-dGTP, preventing mutagenesis by this nucleotide. The enzyme is considered a promising therapeutic target; however, methods to measure its activity are indirect and laborious and have low sensitivity. Here we describe a novel ATP-linked chimeric nucleotide (ARGO) that enables luminescence signaling of the enzymatic reaction, greatly simplifying the measurement of MTH1 activity. We show that the reporting system can be used to identify inhibitors of MTH1, and we use it to quantify enzyme activity in eight cell lines and in colorectal tumor tissue. The ARGO reporter is likely to have considerable utility in the study of the biology of MTH1 and potentially in analyzing patient samples during clinical testing.

Abstract

Mutation in BRCA1/BRCA2 genes accounts for 20% of familial breast cancers, 5% to 10% of which may be due to other less penetrant genes which are still incompletely studied. Herein, a four-gene panel was used to examine the prevalence of BRCA1, BRCA2, TP53, and PTEN in hereditary breast and ovarian cancers in Southern Chinese population. In this cohort, 948 high-risk breast and/or ovarian patients were recruited for genetic screening by next-generation sequencing (NGS). The performance of our NGS pipeline was evaluated with 80 Sanger-validated known mutations and eight negative cases. With appropriate bioinformatics analysis pipeline, the detection sensitivity of NGS is comparable with Sanger sequencing. The prevalence of BRCA1/BRCA2 germline mutations was 9.4% in our Chinese cohort, of which 48.8% of the mutations arose from hotspot mutations. With the use of a tailor-made algorithm, HomopolymerQZ, more mutations were detected compared with single mutation detection algorithm. The frequencies of PTEN and TP53 were 0.21% and 0.53%, respectively, in the Southern Chinese patients with breast and/or ovarian cancers. High-throughput NGS approach allows the incorporation of control cohort that provides an ethnicity-specific data for polymorphic variants. Our data suggest that hotspot mutations screening such as SNaPshot could be an effective preliminary screening alternative adopted in a standard clinical laboratory without NGS setup.

Abstract

Approximately 5%-10% of breast cancers are due to genetic predisposition caused by germline mutations; the most commonly tested genes are BRCA1 and BRCA2 mutations. Some mutations are unique to one family and others are recurrent; the spectrum of BRCA1/BRCA2 mutations varies depending on the geographical origins, populations or ethnic groups. In this review, we compiled data from 11 participating Asian countries (Bangladesh, Mainland China, Hong Kong SAR, Indonesia, Japan, Korea, Malaysia, Philippines, Singapore, Thailand and Vietnam), and from ethnic Asians residing in Canada and the USA. We have additionally conducted a literature review to include other Asian countries mainly in Central and Western Asia. We present the current pathogenic mutation spectrum of BRCA1/BRCA2 genes in patients with breast cancer in various Asian populations. Understanding BRCA1/BRCA2 mutations in Asians will help provide better risk assessment and clinical management of breast cancer.

Abstract

Although a variety of genetic alterations have been found across cancer types, the identification and functional characterization of candidate driver genetic lesions in an individual patient and their translation into clinically actionable strategies remain major hurdles. Here, we use whole genome sequencing of a prostate cancer tumor, computational analyses, and experimental validation to identify and predict novel oncogenic activity arising from a point mutation in the phosphatase and tensin homolog (PTEN) tumor suppressor protein. We demonstrate that this mutation (p.A126G) produces an enzymatic gain-of-function in PTEN, shifting its function from a phosphoinositide (PI) 3-phosphatase to a phosphoinositide (PI) 5-phosphatase. Using cellular assays, we demonstrate that this gain-of-function activity shifts cellular phosphoinositide levels, hyperactivates the PI3K/Akt cell proliferation pathway, and exhibits increased cell migration beyond canonical PTEN loss-of-function mutants. These findings suggest that mutationally modified PTEN can actively contribute to well-defined hallmarks of cancer. Lastly, we demonstrate that these effects can be substantially mitigated through chemical PI3K inhibitors. These results demonstrate a new dysfunction paradigm for PTEN cancer biology and suggest a potential framework for the translation of genomic data into actionable clinical strategies for targeted patient therapy.

Abstract

Gene panels for hereditary breast and ovarian cancer risk assessment are gaining acceptance, even though the clinical utility of these panels is not yet fully defined. Technical questions remain, however, about the performance and clinical interpretation of gene panels in comparison with traditional tests. We tested 1105 individuals using a 29-gene next-generation sequencing panel and observed 100% analytical concordance with traditional and reference data on >750 comparable variants. These 750 variants included technically challenging classes of sequence and copy number variation that together represent a significant fraction (13.4%) of the pathogenic variants observed. For BRCA1 and BRCA2, we also compared variant interpretations in traditional reports to those produced using only non-proprietary resources and following criteria based on recent (2015) guidelines. We observed 99.8% net report concordance, albeit with a slightly higher variant of uncertain significance rate. In 4.5% of BRCA-negative cases, we uncovered pathogenic variants in other genes, which appear clinically relevant. Previously unseen variants requiring interpretation accumulated rapidly, even after 1000 individuals had been tested. We conclude that next-generation sequencing panel testing can provide results highly comparable to traditional testing and can uncover potentially actionable findings that may be otherwise missed. Challenges remain for the broad adoption of panel tests, some of which will be addressed by the accumulation of large public databases of annotated clinical variants.

Abstract

Since its discovery, the BRCA1 tumor suppressor has been shown to play a role in multiple DNA damage response pathways. Here, we will review the involvement of BRCA1 in base-excision DNA repair and highlight its clinical implications.

Abstract

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Colorectal Cancer Screening provide recommendations for selecting individuals for colorectal cancer screening, and for evaluation and follow-up of colon polyps. These NCCN Guidelines Insights summarize major discussion points of the 2015 NCCN Colorectal Cancer Screening panel meeting. Major discussion topics this year were the state of evidence for CT colonography and stool DNA testing, bowel preparation procedures for colonoscopy, and guidelines for patients with a positive family history of colorectal cancer.

Abstract

Breast cancer susceptibility gene 1 (BRCA1) was first identified in 1994 and has since been shown to encode a tumor suppressor protein that maintains genetic stability through DNA damage response pathways. Carriers of mutations in BRCA1 are predisposed to breast and ovarian cancer; however, their cancers lack the targets for existing anticancer drugs. We describe a novel chemoprevention approach that uses DNA repair-activating agents to enhance the repair of oxidative DNA damage and, in turn, prevent tumorigenesis in the presence of mutant BRCA1.

Abstract

To summarize advances in next-generation sequencing and their application to breast and gynecologic cancer risk assessment.Next-generation sequencing panels of 6-112 cancer-associated genes are increasingly used in patient care. Studies report a 4-16% prevalence of mutations other than BRCA1/2 among patients who meet evidence-based practice guidelines for BRCA1/2 testing, with a high rate (15-88%) of uninterpretable variants of uncertain significance. Despite uncertainty about results interpretation and communication, there is early evidence of a benefit from multiple-gene sequencing panels for appropriately selected patients.Multiple-gene sequencing panels appear highly promising for the assessment of breast and gynecologic cancer risk, and they may usefully be administered in the context of cancer genetics expertise and/or clinical research protocols.

Abstract

Lynch syndrome (LS) is an autosomal dominant inherited disorder caused by germline mutations in DNA mismatch repair (MMR) genes. Mutation carriers are at substantially increased risk of developing cancers of the colorectum and endometrium, among others. Given recent recommendations for universal, cost-effective screening of all patients with newly diagnosed colorectal cancer using MMR protein immunohistochemistry, we evaluated MMR protein expression in a series of endometrial cancers in the general population. A total of 605 consecutive cases of primary endometrial cancer at a single institution (1997 to 2013) were evaluated regardless of age, family history, or histologic features. Evaluation methods consisted of immunohistochemistry for the MMR proteins MLH1, MSH2, MSH6, and PMS2, followed by DNA methylation analysis for cases with MLH1/PMS2 deficiency. Germline mutation testing was performed on a subset of cases. Forty MMR-deficient, nonmethylated endometrial cancers were identified: 3 MLH1/PMS2 and 37 MSH6/MSH2 protein deficiencies. Only 25% occurred in women below 50 years of age (range, 39 to 88 y), 1 of which was in a risk-reducing hysterectomy specimen. Only 15% of patients had a prior history of carcinoma, including only 2 patients with prior colorectal carcinoma. Most (80%) of the endometrial cancers were purely endometrioid; there were 2 mixed endometrioid/mucinous, 1 mucinous, 1 serous, 2 clear cell, and 2 carcinosarcoma cases. When grading was applicable, 40% of the endometrial malignancies were FIGO grade 1, 34% grade 2, and 26% grade 3. Thirteen percent arose in the lower uterine segment, and 23% had tumor-infiltrating lymphocytes. Of the tumors with known germline testing, 41% with a LS-associated germline mutation were not associated with any of the traditional indicators that have been recommended for LS screening (ie, age 50 y or younger, personal/family cancer pedigree that meets Bethesda guideline criteria, presence of MMR-associated tumor morphology, or location in the lower uterine segment). These data suggest that a significant number of LS-associated endometrial carcinomas are missed using clinical, histologic, and locational screening parameters and provide support for universal screening of all newly diagnosed endometrial cancers.

Abstract

Germline mutations of the DNA mismatch repair genes MLH1, MSH2, MSH6 or PMS2, and deletions affecting the EPCAM gene adjacent to MSH2, underlie Lynch syndrome by predisposing to early-onset colorectal, endometrial and other cancers. An alternative but rare cause of Lynch syndrome is constitutional epimutation of MLH1, whereby promoter methylation and transcriptional silencing of one allele occurs throughout normal tissues. A dominantly transmitted constitutional MLH1 epimutation has been linked to an MLH1 haplotype bearing two single-nucleotide variants, NM_000249.2: c.-27C>A and c.85G>T, in a Caucasian family with Lynch syndrome from Western Australia. Subsequently, a second seemingly unrelated Caucasian Australian case with the same MLH1 haplotype and concomitant epimutation was reported. We now describe three additional, ostensibly unrelated, cancer-affected families of European heritage with this MLH1 haplotype in association with constitutional epimutation, bringing the number of index cases reported to five. Array-based genotyping in four of these families revealed shared haplotypes between individual families that extended across ≤2.6-≤6.4 megabase regions of chromosome 3p, indicating common ancestry. A minimal ≤2.6 megabase founder haplotype common to all four families was identified, which encompassed MLH1 and additional flanking genes and segregated with the MLH1 epimutation in each family. Our findings indicate that the MLH1 c.-27C>A and c.85G>T variants are borne on a European ancestral haplotype and provide conclusive evidence for its pathogenicity via a mechanism of epigenetic silencing of MLH1 within normal tissues. Additional descendants bearing this founder haplotype may exist who are also at high risk of developing Lynch syndrome-related cancers.

Abstract

Mortality from colorectal cancer can be reduced by early diagnosis and by cancer prevention through polypectomy. These NCCN Guidelines for Colorectal Cancer Screening describe various colorectal screening modalities and recommended screening schedules for patients at average or increased risk of developing colorectal cancer. In addition, the guidelines provide recommendations for the management of patients with high-risk colorectal cancer syndromes, including Lynch syndrome. Screening approaches for Lynch syndrome are also described.

Abstract

To predict the response of breast cancer patients to neoadjuvant chemotherapy (NAC) using features derived from dynamic contrast-enhanced (DCE) MRI.60 patients with triple-negative early-stage breast cancer receiving NAC were evaluated. Features assessed included clinical data, patterns of tumor response to treatment determined by DCE-MRI, MRI breast imaging-reporting and data system descriptors, and quantitative lesion kinetic texture derived from the gray-level co-occurrence matrix (GLCM). All features except for patterns of response were derived before chemotherapy; GLCM features were determined before and after chemotherapy. Treatment response was defined by the presence of residual invasive tumor and/or positive lymph nodes after chemotherapy. Statistical modeling was performed using Lasso logistic regression.Pre-chemotherapy imaging features predicted all measures of response except for residual tumor. Feature sets varied in effectiveness at predicting different definitions of treatment response, but in general, pre-chemotherapy imaging features were able to predict pathological complete response with area under the curve (AUC)=0.68, residual lymph node metastases with AUC=0.84 and residual tumor with lymph node metastases with AUC=0.83. Imaging features assessed after chemotherapy yielded significantly improved model performance over those assessed before chemotherapy for predicting residual tumor, but no other outcomes.DCE-MRI features can be used to predict whether triple-negative breast cancer patients will respond to NAC. Models such as the ones presented could help to identify patients not likely to respond to treatment and to direct them towards alternative therapies.

Abstract

Breast cancer is a common manifestation of an underlying genetic susceptibility to cancer, and 5% to 10% of all breast cancers are associated with a germline mutation in a known risk allele. Detection of mutations has implications for targeted screening and prevention strategies for probands, and for genetic counseling and testing of their family members. This report presents a case involving a 35-year-old woman with no family history of breast or ovarian cancer who presented with a palpable right breast lump. Imaging revealed multiple bilateral breast masses and right axillary adenopathy, and core needle biopsies showed invasive ductal carcinoma in both the right and left breast. This report discusses the appropriate genetics evaluation for a patient with bilateral breast cancer at a young age, including testing for mutations in BRCA1 and BRCA2, followed, if negative, by consideration of testing for mutations in TP53 (Li-Fraumeni syndrome). Given the specialized counseling and testing needs of patients with Li-Fraumeni syndrome, and the implications for targeted screening strategies if a mutation is found, referral to a cancer genetics expert is strongly recommended.

Abstract

The gastric cancer AJCC/UICC staging system recently underwent significant revisions, but studies on Asian patients have reported a lack of adequate discrimination between various consecutive stages. We sought to validate the new system on a U.S. population database.California Cancer Registry data linked to the Office of Statewide Health Planning and Development discharge abstracts were used to identify patients with gastric adenocarcinoma (esophagogastric junction and gastric cardia tumors excluded) who underwent curative-intent surgical resection in California from 2002 to 2006. AJCC/UICC stage was recalculated based on the latest seventh edition. Overall survival probabilities were calculated using the Kaplan-Meier method.Of 1905 patients analyzed, 54 % were males with a median age of 70 years. Median number of pathologically examined lymph nodes was 12 (range, 1-90); 40 % of patients received adjuvant chemotherapy, and 31 % received adjuvant radiotherapy. The seventh edition AJCC/UICC system did not distinguish outcome adequately between stages IB and IIA (P = 0.40), or IIB and IIIA (P = 0.34). By merging stage II into 1 category and moving T2N1 to stage IB and T2N2, T1N3 to stage IIIA, we propose a new grouping system with improved discriminatory abilityIn this first study validating the new seventh edition AJCC/UICC staging system for gastric cancer on a U.S. population with a relatively limited number of lymph nodes examined, we found stages IB and IIA, as well as IIB and IIIA to perform similarly. We propose a revised stage grouping for the AJCC/UICC staging system that better discriminates between outcomes.

Abstract

Experimental targeted treatments for neoadjuvant chemotherapy for triple-negative breast cancer are currently underway, and a current challenge is predicting which patients will respond to these therapies. In this study, we use data from dynamic contrast-enhanced MRI (DCE-MRI) images to predict whether patients with triple negative breast cancer will respond to an experimental neoadjuvant chemotherapy regimen. Using pre-therapy image-based features that are both qualitative (e.g., morphological BI-RADS categories) and quantitative (e.g., lesion texture), we built a model that was able to predict whether patients will have residual invasive cancer with lymph nodes metastases following therapy (receiver operating characteristic area under the curve of 0.83, sensitivity=0.73, specificity=0.83). This model's performance is at a level that is potentially clinically valuable for predicting which patients may or may not benefit from similar treatments in the future.

Abstract

Li-Fraumeni syndrome (LFS) is a rare dominantly inherited cancer predisposition syndrome that was first described in 1969. In most families, it is caused by germline mutations in the TP53 gene and is characterized by early onset of multiple specific cancers and very high lifetime cumulative cancer risk. Despite significant progress in understanding the molecular biology of TP53, the optimal clinical management of this syndrome is poorly defined. We convened a workshop on November 2, 2010, at the National Institutes of Health in Bethesda, Maryland, bringing together clinicians and scientists, as well as individuals from families with LFS, to review the state of the science, address clinical management issues, stimulate collaborative research, and engage the LFS family community. This workshop also led to the creation of the Li-Fraumeni Exploration (LiFE) Research Consortium.

Abstract

Ethnic variations in breast cancer epidemiology and genetics have necessitated investigation of the spectra of BRCA1 and BRCA2 mutations in different populations. Knowledge of BRCA mutations in Chinese populations is still largely unknown. We conducted a multi-center study to characterize the spectra of BRCA mutations in Chinese breast and ovarian cancer patients from Southern China.A total of 651 clinically high-risk breast and/or ovarian cancer patients were recruited from the Hong Kong Hereditary Breast Cancer Family Registry from 2007 to 2011. Comprehensive BRCA1 and BRCA2 mutation screening was performed using bi-directional sequencing of all coding exons of BRCA1 and BRCA2. Sequencing results were confirmed by in-house developed full high resolution DNA melting (HRM) analysis. Among the 451 probands analyzed, 69 (15.3%) deleterious BRCA mutations were identified, comprising 29 in BRCA1 and 40 in BRCA2. The four recurrent BRCA1 mutations (c.470_471delCT, c.3342_3345delAGAA, c.5406+1_5406+3delGTA and c.981_982delAT) accounted for 34.5% (10/29) of all BRCA1 mutations in this cohort. The four recurrent BRCA2 mutations (c.2808_2811delACAA, c.3109C>T, c.7436_7805del370 and c.9097_9098insA) accounted for 40% (16/40) of all BRCA2 mutations. Haplotype analysis was performed to confirm 1 BRCA1 and 3 BRCA2 mutations are putative founder mutations. Rapid HRM mutation screening for a panel of the founder mutations were developed and validated.In this study, our findings suggest that BRCA mutations account for a substantial proportion of hereditary breast/ovarian cancer in Southern Chinese population. Knowing the spectrum and frequency of the founder mutations in this population will assist in the development of a cost-effective rapid screening assay, which in turn facilitates genetic counseling and testing for the purpose of cancer risk assessment.

Abstract

Li-Fraumeni syndrome (LFS) is one of the most penetrant forms of familial cancer susceptibility syndromes, characterized by early age at tumor onset and a wide spectrum of malignant tumors. Identifying LFS in patients with cancer is clinically imperative because they have an increased sensitivity to ionizing radiation and are more likely to develop radiation-induced secondary malignancies. This case report describes a young woman whose initial presentation of LFS was early-onset breast cancer and whose treatment of this primary malignancy with breast conservation likely resulted in a secondary malignancy arising in her radiation field. As seen in this case, most breast cancers in patients with LFS exhibit a triple-positive phenotype (estrogen receptor-positive/progesterone receptor-positive/HER2-positive). Although this patient met classic LFS criteria based on age and personal and family history of cancer, the NCCN Clinical Practice Guidelines in Oncology for Genetic/Familial High-Risk Assessment: Breast and Ovarian Cancer endorse genetic screening for TP53 mutations in a subset of patients with early-onset breast cancer, even in the absence of a suggestive family history, because of the potential for de novo TP53 mutations.

Abstract

Recent literature suggests an increasing incidence of colorectal carcinoma in young patients. We performed a histologic, molecular, and immunophenotypic analysis of patients with sporadic early-onset (≤40 years of age) colorectal carcinoma seen at our institution from the years 2000-2010 and compared these tumors to a cohort of consecutively resected colorectal carcinomas seen in patients >40 years of age. A total of 1160 primary colorectal adenocarcinomas were surgically resected for the years 2000 through 2010. Of these, 75 (6%) were diagnoses in patients ≤40 years of age of which 13 (17%) demonstrated abnormalities in DNA mismatch repair, 4 (5%) were in patients with known germline genetic disorders (two patients with familial adenomatous polyposis, one patient with juvenile polyposis, and one patient with Li-Fraumeni syndrome), and three patients (4%) had long-standing chronic inflammatory bowel disease. The sporadic early-onset colorectal carcinoma group comprised a total of 55 patients (55/1160, 5%) and were compared with a control group comprising 73 consecutively resected colorectal carcinomas with proficient DNA mismatch repair in patients >40 years of age. For the early-onset colorectal carcinoma group, most cases (33/55, 60%) were diagnosed between the age of 35 and 40 years of age. Compared with the control group, the early-onset colorectal carcinoma group was significantly different with respect to tumor location (P<0.007) with 80% (44/55 cases) identified in either the sigmoid colon (24/55, 44%) or rectum (20/55, 36%). Morphologically, early-onset colorectal carcinomas more frequently displayed adverse histologic features compared with the control colorectal carcinoma group such as signet ring cell differentiation (7/55, 13% vs 1/73, 1%, P=0.021), perineural invasion (16/55, 29% vs 8/73, 11%, P=0.009) and venous invasion (12/55, 22% vs 4/73, 6%, P=0.006). A precursor adenomatous lesion was less frequently identified in the early-onset colorectal carcinoma group compared with the control group (19/55, 35% vs 39/73, 53%, P=0.034). Of the early-onset colorectal carcinomas, only 2/45 cases (4%) demonstrated KRAS mutations compared with 11/73 (15%) of the control group colorectal adenocarcinomas harboring KRAS mutations, although this difference did not reach statistical significance (P=0.13). BRAF V600E mutations were not identified in the early-onset colorectal carcinoma group. No difference was identified between the two groups with regard to tumor stage, tumor size, number of lymph node metastases, lymphatic invasion, tumor budding, mucinous histology, or tumor-infiltrating lymphocytes. Both groups had similar recurrence-free (P=0.28) and overall survival (P=0.73). However, patients in the early-onset colorectal carcinoma group more frequently either presented with or developed metastatic disease during their disease course compared with the control colorectal carcinoma group (25/55, 45% vs 18/73, 25%, P=0.014). In addition, 8/55 patients (15%) in the early-onset colorectal carcinoma group developed local recurrence of their tumor while no patients in the control colorectal carcinoma group developed local recurrence (P<0.001), likely due to the increased incidence of rectal carcinoma in the patients with early-onset colorectal carcinoma. Our study demonstrates that colorectal carcinoma is not infrequently diagnosed in patients ≤40 years of age and is not frequently the result of underlying Lynch syndrome or associated with other cancer-predisposing genetic conditions or chronic inflammatory conditions. These tumors have a striking predilection for the distal colon, particularly the sigmoid colon and rectum and are much more likely to demonstrate adverse histologic factors, including signet ring cell differentiation, venous invasion, and perineural invasion.

Abstract

The DNA mismatch repair (MMR) pathway corrects specific types of DNA replication errors that affect microsatellites and thus is critical for maintaining genomic integrity. The genes of the MMR pathway are highly conserved across different organisms. Likewise, defective MMR function universally results in microsatellite instability (MSI) which is a hallmark of certain types of cancer associated with the Mendelian disorder hereditary nonpolyposis colorectal cancer. (Lynch syndrome). To identify previously unrecognized deleted genes or loci that can lead to MSI, we developed a functional genomics screen utilizing a plasmid containing a microsatellite sequence that is a host spot for MSI mutations and the comprehensive homozygous diploid deletion mutant resource for Saccharomyces cerevisiae. This pool represents a collection of non-essential homozygous yeast diploid (2N) mutants in which there are deletions for over four thousand yeast open reading frames (ORFs). From our screen, we identified a deletion mutant strain of the PAU24 gene that leads to MSI. In a series of validation experiments, we determined that this PAU24 mutant strain had an increased MSI-specific mutation rate in comparison to the original background wildtype strain, other deletion mutants and comparable to a MMR mutant involving the MLH1 gene. Likewise, in yeast strains with a deletion of PAU24, we identified specific de novo indel mutations that occurred within the targeted microsatellite used for this screen.

Abstract

Breast cancer is the most common tumor in women with Li-Fraumeni Syndrome (LFS), an inherited cancer syndrome associated with germline mutations in the TP53 tumor suppressor gene. Their lifetime breast cancer risk is 49% by age 60. Breast cancers in TP53 mutation carriers recently have more often been reported to be hormone receptor and HER-2 positive by immunohistochemistry and FISH in small series. We seek to complement the existing small literature with this report of a histopathologic analysis of breast cancers from women with documented LFS. Unstained slides and paraffin-embedded tumor blocks from breast cancers from 39 germline TP53 mutation carriers were assembled from investigators in the LFS consortium. Central histology review was performed on 93% of the specimens by a single breast pathologist from a major university hospital. Histology, grade, and hormone receptor status were assessed by immunohistochemistry; HER-2 status was defined by immunohistochemistry and/or FISH. The 43 tumors from 39 women comprise 32 invasive ductal carcinomas and 11 ductal carcinomas in situ (DCIS). No other histologies were observed. The median age at diagnosis was 32 years (range 22-46). Of the invasive cancers, 84% were positive for ER and/or PR; and 81% were high grade. Sixty three percent of invasive and 73% of in situ carcinomas were positive for Her2/neu (IHC 3+ or FISH amplified). Of the invasive tumors, 53% were positive for both ER and HER2+; other ER/PR/HER2 combinations were observed. The DCIS were positive for ER and HER2 in 27% of the cases. This report of the phenotype of breast cancers from women with LFS nearly doubles the literature on this topic. Most DCIS and invasive ductal carcinomas in LFS are hormone receptor positive and/or HER-2 positive. These findings suggest that modern treatments may result in improved outcomes for women with LFS-associated breast cancer.

Abstract

To improve cancer therapy, it is critical to target metastasizing cells. Circulating tumor cells (CTCs) are rare cells found in the blood of patients with solid tumors and may play a key role in cancer dissemination. Uncovering CTC phenotypes offers a potential avenue to inform treatment. However, CTC transcriptional profiling is limited by leukocyte contamination; an approach to surmount this problem is single cell analysis. Here we demonstrate feasibility of performing high dimensional single CTC profiling, providing early insight into CTC heterogeneity and allowing comparisons to breast cancer cell lines widely used for drug discovery.We purified CTCs using the MagSweeper, an immunomagnetic enrichment device that isolates live tumor cells from unfractionated blood. CTCs that met stringent criteria for further analysis were obtained from 70% (14/20) of primary and 70% (21/30) of metastatic breast cancer patients; none were captured from patients with non-epithelial cancer (n = 20) or healthy subjects (n = 25). Microfluidic-based single cell transcriptional profiling of 87 cancer-associated and reference genes showed heterogeneity among individual CTCs, separating them into two major subgroups, based on 31 highly expressed genes. In contrast, single cells from seven breast cancer cell lines were tightly clustered together by sample ID and ER status. CTC profiles were distinct from those of cancer cell lines, questioning the suitability of such lines for drug discovery efforts for late stage cancer therapy.For the first time, we directly measured high dimensional gene expression in individual CTCs without the common practice of pooling such cells. Elevated transcript levels of genes associated with metastasis NPTN, S100A4, S100A9, and with epithelial mesenchymal transition: VIM, TGFß1, ZEB2, FOXC1, CXCR4, were striking compared to cell lines. Our findings demonstrate that profiling CTCs on a cell-by-cell basis is possible and may facilitate the application of 'liquid biopsies' to better model drug discovery.

Abstract

BRCA1/2 mutation prediction models (BRCAPRO, Myriad II, Couch, Shattuck-Eidens, BOADICEA) are well established in western cohorts to estimate the probability of BRCA1/2 mutations. Results are conflicting in Asian populations. Most studies did not account for gender-specific prediction. We evaluated the performance of these models in a Chinese cohort, including males, before BRCA1/2 mutation testing.The five risk models were used to calculate the probability of BRCA mutations in probands with breast and ovarian cancers; 267 were non-BRCA mutation carriers (247 females and 20 males) and 43 were BRCA mutation carriers (38 females and 5 males).Mean BRCA prediction scores for all models were statistically better for carriers than noncarriers for females but not for males. BRCAPRO overestimated the numbers of female BRCA1/2 mutation carriers at thresholds ≥20% but underestimated if <20%. BRCAPRO and BOADICEA underestimated the number of male BRCA1/2 mutation carriers whilst Myriad II underestimated the number of both male and female carriers. In females, BRCAPRO showed similar discrimination, as measured by the area under the receiver operator characteristic curve (AUC) for BRCA1/2 combined mutation prediction to BOADICEA, but performed better than BOADICEA in BRCA1 mutation prediction (AUC 93% vs. 87%). BOADICEA had the best discrimination for BRCA1/2 combined mutation prediction (AUC 87%) in males.The variation in model performance underscores the need for research on larger Asian cohorts as prediction models, and the possible need for customizing these models for different ethnic groups and genders.

Abstract

To report the outcomes and toxicities in patients treated with intensity-modulated radiotherapy (IMRT) for pancreatic adenocarcinoma.Forty-seven patients with pancreatic adenocarcinoma were treated with IMRT between 2003 and 2008. Of these 47 patients, 29 were treated adjuvantly and 18 definitively. All received concurrent 5-fluorouracil chemotherapy. The treatment plans were optimized such that 95% of the planning target volume received the prescription dose. The median delivered dose for the adjuvant and definitive patients was 50.4 and 54.0 Gy, respectively.The median age at diagnosis was 63.9 years. For adjuvant patients, the 1- and 2-year overall survival rate was 79% and 40%, respectively. The 1- and 2-year recurrence-free survival rate was 58% and 17%, respectively. The local-regional control rate at 1 and 2 years was 92% and 80%, respectively. For definitive patients, the 1-year overall survival, recurrence-free survival, and local-regional control rate was 24%, 16%, and 64%, respectively. Four patients developed Grade 3 or greater acute toxicity (9%) and four developed Grade 3 late toxicity (9%).Survival for patients with pancreatic cancer remains poor. A small percentage of adjuvant patients have durable disease control, and with improved therapies, this proportion will increase. Systemic therapy offers the greatest opportunity. The present results have demonstrated that IMRT is well tolerated. Compared with those who received three-dimensional conformal radiotherapy in previously reported prospective clinical trials, patients with pancreatic adenocarcinoma treated with IMRT in our series had improved acute toxicity.

Abstract

The protein product of the xeroderma pigmentosum group C (XPC) gene is a DNA damage recognition factor that functions early in the process of global genomic nucleotide excision repair. Regulation of XPC expression is governed in part by p53 at the transcriptional level. To identify the regulatory elements involved in the p53-dependent control of XPC expression, we performed a quantitative PCR tiling experiment using multiple regularly spaced primer pairs over an 11-kb region centered around the XPC transcriptional start site. p53 chromatin immunoprecipitation was performed following ultraviolet irradiation, and DNA was analyzed for enrichment at each of 48 amplicons covering this region. A segment just upstream of the XPC translational initiation site was significantly enriched, whereas no enrichment of any other region was noted. In vitro promoter reporter assays and gel retardation assays were used to confirm the p53 responsiveness of this region and to define the minimal region with stimulating activity. We identified a p53 response element that has significant similarity to a consensus sequence, with 3 mismatches. This response element is unique in that part of the p53 binding site included the coding sequence for the first 2 amino acids in the XPC protein.

Abstract

Recent evidence suggests that trastuzumab, a monoclonal antibody which targets HER2, in combination with chemotherapy is a therapeutic option in patients with HER2-positive gastric or gastroesophageal junction cancer. Widely accepted guidelines for HER2 testing in gastric and gastroesophageal junction cancer have not been established. The purpose of this study was to analyze the incidence and patterns of HER2 expression in gastric and gastroesophageal junction cancer using a tissue microarray approach, which closely simulates small biopsies routinely tested for HER2. One hundred sixty-nine patients, including 99 primary gastric adenocarcinomas and 70 primary gastroesophageal junction carcinomas were analyzed for HER2 overexpression by immunohistochemistry and HER2 gene amplification by fluorescence in situ hybridization using scoring schemes proposed by both American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) and the results of the recently published Trastuzumab for Gastric Cancer (ToGA) trial. In our analysis, 19 adenocarcinomas were HER2 positive, defined as either a HER2/CEP17 ratio >2.2 and/or a 3+ HER2 immunohistochemistry score with either the ASCO/CAP or ToGA scoring schemes. Of the 19 HER2-positive adenocarcinomas, 8 (42%) exhibited a characteristic strongly intense basolateral membranous staining pattern which would be interpreted as negative (1+) using the accepted ASCO/CAP scoring scheme for HER2 assessment in breast carcinoma, but were correctly labeled as 3+ positive using the proposed ToGA scoring scheme. Of the 19 HER2-positive adenocarcinomas, 8 (42%) demonstrated heterogeneous HER2 protein expression by immunohistochemistry. Twelve of 99 (12%) gastric carcinomas were positive for HER2. Of these, HER2 was more often identified in intestinal-type adenocarcinomas (10 of 52, 19%) compared with diffuse (2 of 34, 6%) adenocarcinoma. Seven of 70 (10%) gastroesophageal junction carcinomas were positive for HER2 of which all were intestinal type (7 of 58, 12%). HER2 status or primary tumor site did not correlate with patient survival. Gastric and gastroesophageal junction adenocarcinomas typically display a characteristic basolateral membranous pattern of HER2 expression which is often heterogeneous rendering routine evaluation of HER2 status on small tissue samples challenging.

Abstract

For the analysis of cancer, there is great interest in rapid and accurate detection of cancer genome amplifications containing oncogenes that are potential therapeutic targets. The vast majority of cancer tissue samples are formalin fixed and paraffin embedded (FFPE) which enables histopathological examination and long term archiving. However, FFPE cancer genomic DNA is oftentimes degraded and generally a poor substrate for many molecular biology assays. To overcome the issues of poor DNA quality from FFPE samples and detect oncogenic copy number amplifications with high accuracy and sensitivity, we developed a novel approach. Our assay requires nanogram amounts of genomic DNA, thus facilitating study of small amounts of clinical samples. Using droplet digital PCR (ddPCR), we can determine the relative copy number of specific genomic loci even in the presence of intermingled normal tissue. We used a control dilution series to determine the limits of detection for the ddPCR assay and report its improved sensitivity on minimal amounts of DNA compared to standard real-time PCR. To develop this approach, we designed an assay for the fibroblast growth factor receptor 2 gene (FGFR2) that is amplified in a gastric and breast cancers as well as others. We successfully utilized ddPCR to ascertain FGFR2 amplifications from FFPE-preserved gastrointestinal adenocarcinomas.

Abstract

We report a rare synchronous presentation of adrenocortical carcinoma (ACC) and papillary thyroid carcinoma (PTC). A 31-year-old male first presented with a large left adrenal mass that was identified during the workup for refractory hypertension due to hyperaldosteronism. The mass was removed surgically with pathology showing ACC. The patient was then treated with adjuvant radiation therapy and mitotane chemotherapy. Four months post ACC resection, metastatic ACC to the right upper lung and PTC in the left lobe of the thyroid were found in surveillance imaging. He subsequently developed pulmonary, contralateral adrenal and brain metastases from his ACC. Li Fraumeni syndrome and Multiple Endocrine Neoplasia Type I (MEN I) were considered, but testing of both P53 and menin genes showed no mutation. We also performed a review of the literature and found three similar cases, however gene mutation analysis was not performed..

Abstract

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant cancer syndrome. Up to 30% of families with HDGC have mutations in the E-cadherin gene, CDH1. The role of prophylactic versus therapeutic gastrectomy for HDGC was studied prospectively.Eighteen consecutive patients with CDH1 mutations and positive family history were studied prospectively, including 13 without and 5 with symptoms. Proportions were compared by Fisher's exact test, and survival by the Breslow modification of the Wilcoxon rank-sum test.Each patient underwent total gastrectomy (TG), and 17 (94%) were found to have signet ring cell adenocarcinoma. Twelve of 13 asymptomatic patients had T1, N0 cancer, and only 2/12 (16%) had it diagnosed preoperatively despite state-of-the-art screening methods. Each asymptomatic patient did well postoperatively, and no patient has recurred. For five symptomatic patients, each (100%) was found to have signet ring cell adenocarcinoma (P = 0.002 versus asymptomatic) by preoperative endoscopy; three (60%) had lymph node involvement and two (40%) had distant metastases at time of operation. Two-year survival was 100% for asymptomatic and 40% for symptomatic patients (P

Abstract

This Phase II trial evaluated the toxicity, local control, and overall survival in patients treated with sequential gemcitabine and linear accelerator-based single-fraction stereotactic body radiotherapy (SBRT).Twenty patients with locally advanced, nonmetastatic pancreatic adenocarcinoma were enrolled on this prospective single-institution, institutional review board-approved study. Gemcitabine was administered on Days 1, 8, and 15, and SBRT on Day 29. Gemcitabine was restarted on Day 43 and continued for 3-5 cycles. SBRT of 25 Gy in a single fraction was delivered to the internal target volume with a 2- 3-mm margin using a nine-field intensity-modulated radiotherapy technique. Respiratory gating was used to account for breathing motion. Follow-up evaluations occurred at 4-6 weeks, 10-12 weeks, and every 3 months after SBRT.All patients completed SBRT and a median of five cycles of chemotherapy. Follow-up for the 2 remaining alive patients was 25.1 and 36.4 months. No acute Grade 3 or greater nonhematologic toxicity was observed. Late Grade 3 or greater toxicities occurred in 1 patient (5%) and consisted of a duodenal perforation (G4). Three patients (15%) developed ulcers (G2) that were medically managed. Overall, median survival was 11.8 months, with 1-year survival of 50% and 2-year survival of 20%. Using serial computed tomography, the freedom from local progression was 94% at 1 year.Linear accelerator-delivered SBRT with sequential gemcitabine resulted in excellent local control of locally advanced pancreatic cancer. Future studies will address strategies for reducing long-term duodenal toxicity associated with SBRT.

Abstract

The purpose of this study was to compare outcomes in patients with anal canal squamous cell carcinoma (SCCA) who were treated with definitive chemoradiotherapy by either intensity-modulated radiation therapy (IMRT) or conventional radiotherapy (CRT).Forty-six patients who received definitive chemoradiotherapy from January 1993 to August 2009 were included. Forty-five patients received 5-fluorouracil with mitomycin C (n = 39) or cisplatin (n = 6). Seventeen (37%) were treated with CRT and 29 (63%) with IMRT. The median dose was 54 Gy in both groups. Median follow-up was 26 months (CRT) and 32 months (IMRT). T3-T4 stage (P = .18) and lymph node-positive disease (P = .6) were similar between groups.The CRT group required longer treatment duration (57 days vs 40 days, P < .0001), more treatment breaks (88% vs 34.5%, P = .001), and longer breaks (12 days vs 1.5 days, P < .0001) than patients treated with IMRT. Eleven (65%) patients in the CRT group experienced grade >2 nonhematologic toxicity compared with 6 (21%) patients in the IMRT group (P = .003). The 3-year overall survival (OS), locoregional control (LRC), and progression-free survival were 87.8%, 91.9%, and 84.2%, respectively, for the IMRT groups and 51.8%, 56.7%, and 56.7%, respectively, for the CRT group (all P < .01). On multivariate analysis, T stage, use of IMRT, and treatment duration were associated with OS, and T stage and use of IMRT were associated with LRC.The use of IMRT was associated with less toxicity, reduced need for treatment breaks, and excellent LRC and OS compared with CRT in patients with SCCA of the anal canal.

Abstract

Mismatch repair protein immunohistochemistry is a widely used method for detecting patients at risk for Lynch syndrome. Recent data suggest that a two-antibody panel approach using PMS2 and MSH6 is an effective screening protocol for colorectal carcinoma, but there are limited data concerning this approach for extraintestinal tumors. The purpose of this study was to review the utility of a two-antibody panel approach in colorectal carcinoma and extraintestinal tumors. We evaluated mismatch repair protein expression in two cohorts: (1) a retrospective analysis of intestinal and extraintestinal tumors (n=334) tested for mismatch repair protein immunohistochemistry and (2) a prospectively accrued series of intestinal, gynecologic tract, and skin sebaceous neoplasms (n=98). A total of 432 cases were analyzed, including 323 colorectal, 50 gynecologic tract, 49 skin sebaceous, and 10 other neoplasms. Overall, 102/432 tumors (24%) demonstrated loss of at least one mismatch repair protein. Concurrent loss of MLH1 and PMS2 was the most common pattern of abnormal expression (50/432, 12%) followed by concurrent loss of MSH2 and MSH6 (33/432, 8%). Of 55 cases with abnormal PMS2 expression, 5 (9%) demonstrated isolated loss of PMS2 expression. Of 47 cases with abnormal MSH6 expression, 14 (30%) demonstrated isolated loss of MSH6 expression. Isolated loss of MLH1 or MSH2 was not observed. Colorectal carcinomas more frequently demonstrated abnormal expression of PMS2 (39/59, 66%). Skin sebaceous neoplasms more frequently demonstrated abnormal expression of MSH6 (18/24, 75%, respectively). A total of 65 tumors with abnormal mismatch repair protein expression were tested for microsatellite instability (MSI): 47 (72%) MSI high, 9 (14%) MSI low, and 9 (14%) microsatellite stable (MSS). Abnormal MSH6 expression accounted for 14/18 (78%) cases that were MSS or MSI low. Our findings confirm the utility of a two-antibody approach using PMS2 and MSH6 in colorectal carcinoma and indicate that this approach is effective in extraintestinal neoplasms associated with Lynch syndrome.

Abstract

Germline mutations in the two breast cancer susceptibility genes, BRCA1 and BRCA2 account for a significant portion of hereditary breast/ovarian cancer. De novo mutations such as multiple exon deletion are rarely occurred in BRCA1 and BRCA2. During our mutation screening for BRCA1/2 genes to Chinese women with risk factors for hereditary breast/ovarian cancer, we identified a novel germline mutation, consisting of a deletion from exons 1 to 12 in BRCA1 gene, in a patient diagnosed with early onset triple negative breast cancer with no family history of cancer. None of her parents carried the mutation and molecular analysis showed that this novel de novo germline mutation resulted in down-regulation of BRCA1 gene expression.

Abstract

Germline mutations in CDH1 are associated with hereditary diffuse gastric cancer; lobular breast cancer also occurs excessively in families with such condition.To determine if CDH1 is a susceptibility gene for lobular breast cancer in women without a family history of diffuse gastric cancer, germline DNA was analysed for the presence of CDH1 mutations in 318 women with lobular breast cancer who were diagnosed before the age of 45 years or had a family history of breast cancer and were not known, or known not, to be carriers of germline mutations in BRCA1 or BRCA2. Cases were ascertained through breast cancer registries and high-risk cancer genetic clinics (Breast Cancer Family Registry, the kConFab and a consortium of breast cancer genetics clinics in the United States and Spain). Additionally, Multiplex Ligation-dependent Probe Amplification was performed for 134 cases to detect large deletions.No truncating mutations and no large deletions were detected. Six non-synonymous variants were found in seven families. Four (4/318 or 1.3%) are considered to be potentially pathogenic through in vitro and in silico analysis.Potentially pathogenic germline CDH1 mutations in women with early-onset or familial lobular breast cancer are at most infrequent.

Abstract

Poly (ADP-ribose) polymerase (PARP) inhibitors, a novel class of drugs that target tumors with DNA repair defects, have received tremendous enthusiasm. Early preclinical studies identified BRCA1 and BRCA2 tumors to be highly sensitive to PARP inhibitors as a result of homologous recombination defect. Based on this premise, PARP inhibitors have been tested in early phase clinical trials as a single agent in BRCA1 or BRCA2 mutation carriers and in combination with chemotherapy in triple-negative breast cancer patients. For high-risk populations, use of PARP inhibition as a prevention agent has been postulated, but no robust preclinical or clinical studies exist yet. We review the preclinical and clinical studies in treatment of breast cancer and rationale for use of PARP inhibitors as a prevention agent for high-risk populations. Of significance, PARP inhibitors vary significantly in mechanism of action, dosing intervals, and toxicities, which are highlighted in this review.

Abstract

Pancreatic cancer is associated with mutations in the tumor suppressor gene cyclin-dependent kinase inhibitor 2A (p16(INK4A) ), a regulator of the cell cycle and apoptosis. This study investigates whether immunohistochemical expression of p16(INK4A) as well as hypoxia markers and poly adenosine diphosphate-ribose polymerase (PARP) correlates with survival in patients with resected pancreatic adenocarcinoma.Seventy-three patients with pancreatic adenocarcinoma who underwent curative resection at Stanford University were included. From the surgical specimens, a tissue microarray was constructed using triplicate tissue cores from the primary tumor and used for immunohistochemical staining for the following markers: carbonic anhydrase IX, dihydrofolate reductase, p16(INK4A) , and PARP1/2. Staining was scored as either positive or negative and percentage positive staining. Staining score was correlated with overall survival (OS) and progression-free survival (PFS).Of the markers tested, only immunohistochemical expression of p16(INK4A) correlated with clinical outcome. On univariate analysis, p16(INK4A) expression in the tumor was associated with improved OS (P = .038) but not PFS (P = .28). The median survival for patients with positive versus negative p16(INK4A) staining was 28.8 months versus 18 months. On multivariate analysis, p16(INK4A) expression was associated with improved OS (P = .026) but not PFS (P = .25). Age (P = .0019) and number of nodes involved (P = .025) were also significant for OS. Adjuvant chemotherapy and margin status did not correlate with OS or PFS.Expression of p16(INK4A) is associated with improved OS in patients with resected pancreatic adenocarcinoma. Further investigation is needed for validation, given conflicting data in the published literature. .

Abstract

In contrast to endocrine-sensitive and human epidermal growth factor receptor 2 (HER2)-positive breast cancer, novel agents capable of treating advanced triple-negative breast cancer (TNBC) are lacking. Poly(ADP-ribose) polymerase (PARP) inhibitors are emerging as one of the most promising "targeted" therapeutics to treat TNBC, with the intended "target" being DNA repair. PARPs are a family of enzymes involved in multiple cellular processes, including DNA repair. TNBC shares multiple clinico-pathologic features with BRCA-mutated breast cancers, which harbor dysfunctional DNA repair mechanisms. Investigators hypothesized that PARP inhibition, in conjunction with the loss of DNA repair via BRCA-dependent mechanisms, would result in synthetic lethality and augmented cell death. This hypothesis has borne out in both preclinical models and in clinical trials testing PARP inhibitors in both BRCA-deficient and triple-negative breast cancer. The focus of this review includes an overview of the preclinical rationale for evaluating PARP inhibitors in TNBC, the presumed mechanism of action of this novel therapeutic class, promising results from several influential clinical trials of PARP inhibition in advanced breast cancer (both TNBC and BRCA deficient), proposed mechanisms of acquired resistance to PARP inhibitors, and, finally, concludes with current challenges and future directions for the development of PARP inhibitors in the treatment of breast cancer.

Abstract

The therapeutic implications of DNA damage in cancer therapy have long been appreciated and form the basis of many successful cytotoxic chemotherapy and radiotherapy treatment strategies. A novel class of DNA repair defect targeted therapeutics that inhibit poly (ADP-Ribose) polymerase (PARP) are being rapidly developed in breast cancer based on exciting preliminary clinical activity as single agents in BRCA mutation-associated breast cancer and in combination with chemotherapy in triple-negative breast cancer. Though there is widespread enthusiasm to move these drugs forward quickly, much remains to be understood about the optimal use of the novel agents. Here we review the clinical development of PARP inhibitors in breast cancer and highlight clinical trials in progress. We also provide commentary on a series of outstanding questions in the field, the answers to which will be critical for the successful development of PARP inhibitor-based strategies in early- and late-stage breast cancer.

Abstract

The current study was performed to compare the clinical outcomes and toxicity in patients treated with postoperative chemoradiotherapy for gastric cancer using intensity-modulated radiotherapy (IMRT) versus 3-dimensional conformal radiotherapy (3D CRT).Fifty-seven patients with gastric or gastroesophageal junction cancer were treated postoperatively: 26 with 3D CRT and 31 with IMRT. Concurrent chemotherapy was capecitabine (n=31), 5-fluorouracil (5-FU) (n=25), or none (n=1). The median radiation dose was 45 Gy. Dose volume histogram parameters for kidney and liver were compared between treatment groups.The 2-year overall survival rates for 3D CRT versus IMRT were 51% and 65%, respectively (P=.5). Four locoregional failures occurred each in the 3D CRT (15%) and the IMRT (13%) patients. Grade>or=2 acute gastrointestinal toxicity was found to be similar between the 3D CRT and IMRT patients (61.5% vs 61.2%, respectively) but more treatment breaks were needed (3 vs 0, respectively). The median serum creatinine from before radiotherapy to most recent creatinine was unchanged in the IMRT group (0.80 mg/dL) but increased in the 3D CRT group from 0.80 mg/dL to 1.0 mg/dL (P=.02). The median kidney mean dose was higher in the IMRT versus the 3D CRT group (13.9 Gy vs 11.1 Gy; P=.05). The median kidney V20 was lower for the IMRT versus the 3D CRT group (17.5% vs 22%; P=.17). The median liver mean dose for IMRT and 3D CRT was 13.6 Gy and 18.6 Gy, respectively (P=.19). The median liver V30 was 16.1% and 28%, respectively (P

Abstract

Our patient was a 52-year-old man who was diagnosed with signet ring cell gastric adenocarcinoma. An extensive family history of gastric cancer raised suspicion for hereditary diffuse gastric cancer. Sequencing of the patient's CDH1 gene revealed a novel point mutation in a strictly conserved splice site within intron 6, c.833-2 A > G. This mutation was predicted to result in loss of function due to defective RNA splicing. To characterize the pathogenic mechanism of this mutation, we amplified the patient's CDH1 gene products by reverse transcriptase polymerase chain reaction. Primers flanking the region of the mutation detected 3 distinct transcripts. In addition to the wild-type product, a larger product consistent with activation of a cryptic splice site within intron 6 and a smaller product shown to result from exon 7 skipping were detected. In summary, we have identified a novel CDH1 mutation in a large hereditary diffuse gastric cancer kindred and identified its pathogenic mechanism.

Abstract

The aim of this study was to investigate the effect of preoperative chemoradiotherapy (CRT) on nodal disease in locally advanced rectal adenocarcinoma.Thirty-two patients staged uT3N0 and 27 patients staged uT3N1 rectal adenocarcinoma who underwent pre-CRT staging using endoscopic ultrasound or rectal protocol CT were included. The median radiation dose was 50.4 Gy (range: 45-50.4 Gy) at 1.8 Gy per fraction and all patients received concurrent 5-FU or capecitabine-based chemotherapy. Low anterior resection or abdomino-perineal resection occurred at a median of 46 days (range: 27-112 days) after CRT.Eleven of 32 uT3N0 patients (34.4%) and 13 of 26 uT3N1 patients (50.0%) had ypN+ (P = 0.29). For patients with uT3N0, 10 of 20 (50.0%) with ypT2-3 and 1 of 12 (8.3%) with ypT0-1 were ypN+ (P = 0.02). For patients with uT3N1, 12 of 20 (60.0%) with ypT2-3 and 1 of 6 (16.7%) with ypT0-1 were ypN+ (P = 0.16). Overall, the ypN+ rate was 11.1% in the ypT0-yT1 group compared with 55.0% in the ypT2-yT3 group (P = 003). Among patients with uT3N0 disease, the ypN+ rate in patients who had surgery > 46 days vs 46 days vs 46 days vs

Abstract

Triple-negative breast cancers share an aggressive biology, marked by increased recurrence risk and poorer survival compared with hormone receptor-positive subtypes. Few therapeutic trials have specifically focused on triple-negative breast cancer, and the treatment of patients with early-stage triple-negative breast cancer has changed little in the past decade. Over this time, however, attention has shifted to treatment approaches based on molecular subtypes of breast cancer, and investigation into the mechanistic underpinnings of these distinct subtypes has exploded. Converging preclinical rationales combined with early provocative clinical efficacy has focused recent attention on strategies targeting DNA repair defects for the treatment of patients with triple-negative and BRCA mutation-associated breast cancers. These developments are very promising and suggest that major advances in the targeted treatment of patients with triple-negative breast cancer are in sight. This review provides an overview of the clinical features of triple-negative breast cancer and current treatment strategies in the adjuvant setting. Mechanisms of DNA repair and the DNA damage response are reviewed to provide background for understanding novel approaches targeting DNA repair defects in this disease with DNA-damaging chemotherapeutic agents and poly(ADP-ribose) polymerase inhibitors. Ongoing studies, including those investigating the role of antiangiogenic therapies, are also reviewed.

Abstract

Telomeres cap the ends of chromosomes and are composed of a series of noncoding hexamer repeats. Telomeres protect the integrity of DNA coding sequences and are integral to the maintenance of genomic stability. Previous studies have shown an association between shortened lymphocyte telomeres and increased risk for specific cancers. However, the association between telomere length and breast cancer risk is less clear. We examined the relative telomere length (RTL) in blood from women with no personal or family history of cancer (controls) compared with different populations of women with breast cancer and women at high genetic risk for developing breast cancer. RTL was determined as the telomere to single gene copy number ratio assessed by quantitative PCR. Breast cancer cases (low risk, n = 40; high risk, n = 62) had significantly longer RTL compared with unaffected controls (n = 50; mean RTL = 1.11 versus 0.84; P < 0.0001). The assessment of risk by RTL quartile showed an increased risk for breast cancer with each longer quartile, with the most significant risk observed in the longest quartile (odds ratio, 23.3; confidence interval, 4.4-122.3; P < 0.0003). Women without breast cancer but at high risk due to family history (n = 30) also showed longer telomeres than controls (mean RTL = 1.09 versus 0.84; P < 0.0001). Our analysis supports previous findings of longer RTL in breast cancer cases compared with controls, and is the first to observe longer RTL in women without breast cancer identified as high risk based on family history.

Abstract

Malignant astrocytomas are a deadly solid tumor in children. Limited understanding of their underlying genetic basis has contributed to modest progress in developing more effective therapies. In an effort to identify such alterations, we performed a genome-wide search for DNA copy number aberrations (CNA) in a panel of 33 tumors encompassing grade 1 through grade 4 tumors. Genomic amplifications of 10-fold or greater were restricted to grade 3 and 4 astrocytomas and included the MDM4 (1q32), PDGFRA (4q12), MET (7q21), CMYC (8q24), PVT1 (8q24), WNT5B (12p13), and IGF1R (15q26) genes. Homozygous deletions of CDKN2A (9p21), PTEN (10q26), and TP53 (17p3.1) were evident among grade 2 to 4 tumors. BRAF gene rearrangements that were indicated in three tumors prompted the discovery of KIAA1549-BRAF fusion transcripts expressed in 10 of 10 grade 1 astrocytomas and in none of the grade 2 to 4 tumors. In contrast, an oncogenic missense BRAF mutation (BRAF(V600E)) was detected in 7 of 31 grade 2 to 4 tumors but in none of the grade 1 tumors. BRAF(V600E) mutation seems to define a subset of malignant astrocytomas in children, in which there is frequent concomitant homozygous deletion of CDKN2A (five of seven cases). Taken together, these findings highlight BRAF as a frequent mutation target in pediatric astrocytomas, with distinct types of BRAF alteration occurring in grade 1 versus grade 2 to 4 tumors.

Abstract

Pancreatic cancer continues to prove difficult to clinically diagnose. Multiple simultaneous measurements of plasma biomarkers can increase sensitivity and selectivity of diagnosis. Proximity ligation assay (PLA) is a highly sensitive technique for multiplex detection of biomarkers in plasma with little or no interfering background signal.We examined the plasma levels of 21 biomarkers in a clinically defined cohort of 52 locally advanced (Stage II/III) pancreatic ductal adenocarcinoma cases and 43 age-matched controls using a multiplex proximity ligation assay. The optimal biomarker panel for diagnosis was computed using a combination of the PAM algorithm and logistic regression modeling. Biomarkers that were significantly prognostic for survival in combination were determined using univariate and multivariate Cox survival models.Three markers, CA19-9, OPN and CHI3L1, measured in multiplex were found to have superior sensitivity for pancreatic cancer vs. CA19-9 alone (93% vs. 80%). In addition, we identified two markers, CEA and CA125, that when measured simultaneously have prognostic significance for survival for this clinical stage of pancreatic cancer (p < 0.003).A multiplex panel assaying CA19-9, OPN and CHI3L1 in plasma improves accuracy of pancreatic cancer diagnosis. A panel assaying CEA and CA125 in plasma can predict survival for this clinical cohort of pancreatic cancer patients.

Abstract

Childhood leukemia, which accounts for >30% of newly diagnosed childhood malignancies, is one of the leading causes of death for children with cancer. Genome-wide studies using microarray chips to identify copy number changes in human cancer are becoming more common. In this pilot study, 45 pediatric leukemia samples were analyzed for gene copy aberrations using novel molecular inversion probe (MIP) technology. Acute leukemia subtypes included precursor B-cell acute lymphoblastic leukemia (ALL) (n=23), precursor T-cell ALL (n=6), and acute myeloid leukemia (n=14). The MIP analysis identified 69 regions of recurring copy number changes, of which 41 have not been identified with other DNA microarray platforms. Copy number gains and losses were validated in 98% of clinical karyotypes and 100% of fluorescence in situ hybridization studies available. We report unique patterns of copy number loss in samples with 9p21.3 (CDKN2A) deletion in the precursor B-cell ALL patients, compared with the precursor T-cell ALL patients. MIPs represent an attractive technology for identifying novel copy number aberrations, validating previously reported copy number changes, and translating molecular findings into clinically relevant targets for further investigation.

Abstract

The retinoblastoma Rb/E2F tumor suppressor pathway plays a major role in the regulation of mammalian cell cycle progression. The pRb protein, along with closely related proteins p107 and p130, exerts its anti-proliferative effects by binding to the E2F family of transcription factors known to regulate essential genes throughout the cell cycle. We sought to investigate the role of the Rb/E2F1 pathway in the lesion recognition step of nucleotide excision repair (NER) in mouse embryonic fibroblasts (MEFs). Rb-/-, p107-/-, p130-/- MEFs repaired both cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs) at higher efficiency than did wildtype cells following UV-C irradiation. The expression of damaged DNA binding gene DDB2 involved in the DNA lesion recognition step was elevated in the Rb family-deficient MEFs. To determine if the enhanced DNA repair in the absence of the Rb gene family is due to the derepression of E2F1, we assayed the ability of E2F1-deficient cells to repair damaged DNA and demonstrated that E2F1-/- MEFs are impaired for the removal of both CPDs and 6-4PPs. Furthermore, wildtype cells induced a higher expression of DDB2 and xeroderma pigmentosum gene XPC transcript levels than did E2F1-/- cells following UV-C irradiation. Using an E2F SiteScan algorithm, we uncovered a putative E2F-responsive element in the XPC promoter upstream of the transcription start site. We showed with chromatin immunoprecipitation assays the binding of E2F1 to the XPC promoter in a UV-dependent manner, suggesting that E2F1 is a transcriptional regulator of XPC. Our study identifies a novel E2F1 gene target and further supports the growing body of evidence that the Rb/E2F1 tumor suppressor pathway is involved in the regulation of the DNA lesion recognition step of nucleotide excision repair.

Abstract

The authors report on the local control and toxicity of stereotactic body radiotherapy (SBRT) for patients with unresectable pancreatic adenocarcinoma.Seventy-seven patients with unresectable adenocarcinoma of the pancreas received 25 gray (Gy) in 1 fraction. Forty-five patients (58%) had locally advanced disease, 11 patients (14%) had medically inoperable disease, 15 patients (19%) had metastatic disease, and 6 patients (8%) had locally recurrent disease. Nine patients (12%) had received prior chemoradiotherapy. Sixteen patients (21%) received between 45 to 54 Gy of fractionated radiotherapy and SBRT. Various gemcitabine-based chemotherapy regimens were received by 74 patients (96%), but 3 patients (4%) did not receive chemotherapy until they had distant failure.The median follow-up was 6 months (range, 3-31 months) and, among surviving patients, it was 12 months (range, 3-31 months). The overall rates of freedom from local progression (FFLP) at 6 months and 12 months were 91% and 84%, respectively. The 6- and 12-month isolated local recurrence rates were 5% and 5%, respectively. There was no difference in the 12-month FFLP rate based on tumor location (head/uncinate, 91% vs body/tail, 86%; P = .52). The progression-free survival (PFS) rates at 6 months and 12 months were 26% and 9%, respectively. The PFS rate at 6 months was superior for patients who had nonmetastatic disease versus patients who had metastatic disease (28% vs 15%; P = .05). The overall survival (OS) rates at 6 months and 12 months from SBRT were 56% and 21%, respectively. Four patients (5%) experienced grade > or = 2 acute toxicity. Three patients (4%) experienced grade 2 late toxicity, and 7 patients (9%) experienced grade > or = 3 late toxicity. At 6 months and 12 months, the rates of grade > or = 2 late toxicity were 11% and 25%, respectively.SBRT for pancreatic adenocarcinoma was effective for local control with associated risk of toxicity and should be used with rigorous attention to quality assurance. Efforts to reduce complications are warranted. Distant metastases account for the vast majority of disease-related mortality.

Abstract

Fractionated radiotherapy and chemotherapy for locally advanced pancreatic cancer achieves only modest local control. This prospective trial evaluated the efficacy of a single fraction of 25 Gy stereotactic body radiotherapy (SBRT) delivered between Cycle 1 and 2 of gemcitabine chemotherapy.A total of 16 patients with locally advanced, nonmetastatic, pancreatic adenocarcinoma received gemcitabine with SBRT delivered 2 weeks after completion of the first cycle. Gemcitabine was resumed 2 weeks after SBRT and was continued until progression or dose-limiting toxicity. The gross tumor volume, with a 2-3-mm margin, was treated in a single 25-Gy fraction by Cyberknife. Patients were evaluated at 4-6 weeks, 10-12 weeks, and every 3 months after SBRT.All 16 patients completed SBRT. A median of four cycles (range one to nine) of chemotherapy was delivered. Three patients (19%) developed local disease progression at 14, 16, and 21 months after SBRT. The median survival was 11.4 months, with 50% of patients alive at 1 year. Patients with normal carbohydrate antigen (CA)19-9 levels either at diagnosis or after Cyberknife SBRT had longer survival (p <0.01). Acute gastrointestinal toxicity was mild, with 2 cases of Grade 2 (13%) and 1 of Grade 3 (6%) toxicity. Late gastrointestinal toxicity was more common, with five ulcers (Grade 2), one duodenal stenosis (Grade 3), and one duodenal perforation (Grade 4). A trend toward increased duodenal volumes radiated was observed in those experiencing late effects (p = 0.13).SBRT with gemcitabine resulted in comparable survival to conventional chemoradiotherapy and good local control. However, the rate of duodenal ulcer development was significant.

Abstract

Ovarian malignancies occurring in the setting of hereditary nonpolyposis colorectal carcinoma syndrome typically present in young women, often as the first or "sentinel" cancer, but the frequency of microsatellite instability (MSI) and mismatch repair (MMR) defects in ovarian surface epithelial malignancies in women

Abstract

Women with mutations in the BRCA1 or BRCA2 cancer susceptibility genes face unique choices regarding management of their high risk for breast and ovarian cancer that impact their reproductive options. In order to explore women's preferences for management of elevated cancer risk, we evaluated the decisions of BRCA1/2 mutation carriers about contraception, prophylactic surgery, and family planning.An internet-based questionnaire assessing high-risk women's preferences about cancer risk management and reproductive options was designed, pilot-tested and administered electronically to 284 participants of an internet-based advocacy group for women with BRCA1/2 mutations.Two hundred and thirteen eligible participants completed the majority of the survey. Mean age was 34 years; 66% were BRCA1 mutation carriers and 34% were BRCA2 mutation carriers. Most women (92%) had used oral contraceptive pills. About 88% of responders reported frequent or extreme worry about transmitting the mutation to their children. Despite their high level of worry, few responders said they would likely consider using assisted reproduction technologies such as a pregnancy surrogate (3%), cryopreservation of oocytes or embryos (8%), or pre-implantation genetic diagnosis (PGD) to select embryos without BRCA1/2 mutations (13%).Although they expressed substantial concern about transmitting BRCA1/2 mutations to their children, only a minority of the high-risk women surveyed were likely to consider currently available assisted reproductive strategies. Further research is necessary to explore the risk management preferences of patients with inherited cancer predisposition, and to incorporate these preferences into clinical care.

Abstract

Hereditary diffuse gastric cancer is a rare autosomal dominant cancer susceptibility syndrome caused by germline E-cadherin (CDH1) mutations in 40% of cases with a high degree of penetrance. Screening endoscopy has not been useful in identifying early cancer, in part owing to conflicting data concerning site(s) of involvement in the stomach and the lack of endoscopically detectable pathology. Risk-reducing total gastrectomy specimens from 8 asymptomatic adults with germline mutations in the CDH1 gene (3 different pedigrees) were studied using a sequential serial sectioning protocol with submission of the entire stomach for histologic analysis. The presence, size, and distribution of signet ring cell clusters were determined for each section and geographic maps of the invasive foci were constructed and compared with gastrectomy specimens from patients with germline E-cadherin mutation and symptomatic gastric cancer. All but 1 of the asymptomatic patients with germline mutations in the CDH1 gene had negative endoscopic screening. All risk-reducing gastrectomy specimens were macroscopically normal. All contained multiple foci (mean, 10.9) of microscopic intramucosal signet ring cell carcinoma confined to the superficial gastric mucosa; no invasion of submucosa was identified. In situ carcinoma was present in 6/8 cases. The majority of signet ring foci were located in the proximal one third of the stomach, most within oxyntic-type mucosa. The number and size of foci were not related to age, but there was a trend toward more severe disease burden in women. Stomachs from the symptomatic group of patients with germline CDH1 mutations exhibited infiltrative foci with higher Ki-67 labeling that extended well beyond the superficial mucosa. In addition, while superficial signet ring cancer exhibited decreased or absent E-cadherin and beta-catenin protein expression in all cases studied, deeply invasive signet ring cancer showed reversion to E-cadherin and beta-catenin protein expression in a subset of mutation carriers. Our study indicates that superficial intramucosal signet ring carcinoma, although widespread, is predominantly located in the proximal one third of the stomach in patients with E-cadherin gene mutations. The observed site predilection suggests a possible role for geographically targeted endoscopic surveillance biopsy in patients who elect to delay surgical intervention.

Abstract

Germline mutations of BRCA1 and BRCA2 account for the majority of hereditary breast cancers, many of which are classified as variants of unknown significance (VUS). We report the identification of a novel BRCA2 variant (c.7806-9T > G) in a Chinese family with multiple breast cancers and document it as a pathogenic mutation.The proband in this family was diagnosed with breast cancer at age 50 with a strong family history of breast cancer. DNA and RNA were extracted from the blood of the proband and her family, and was used for BRCA gene mutation/deletion screening and RNA splicing analysis.BRCA2 c.7806-9T > G was identified in the proband, which was suggestive of a variant. This change was also found in two sisters of the proband with a history of breast cancer, as well as from the proband's maternal gastric cancer. The only sibling free of breast cancer did not carry the BRCA2 variant, thus demonstrating that the mutation segregates with the clinical phenotype in this family. RNA analysis on the proband blood sample revealed three aberrant splicing variants: c.7806_7874del, c.7806_7976del, and c.7806-8_7806-1ins. The latter causes a frameshift and creates a truncated protein, whilst the other two splicing variants resulted in shorter forms of the protein.The identified BRCA2 c.7806-9T > G [Genbank: DQ889340] was found to be pathogenic, based on aberrant splicing events resulting in the formation of truncated protein products. Thus, better understanding and classification of BRCA variants as neutral or disease causing has important implications for genetic counseling so that appropriate management can be given.

Abstract

We describe a 2-year-old female with a completely resected cerebral pilocytic astrocytoma who subsequently developed B-progenitor acute lymphoblastic leukemia (ALL). Her father and paternal uncle were previously diagnosed with glioblastoma multiforme. Sequence analysis of the patient's p53 gene revealed a novel germline three base-pair deletion (339_341delCTT) in exon 4, resulting in removal of an evolutionarily conserved phenylalanine amino acid residue at codon 113. The same mutation was found in the patient's two clinically unaffected siblings. The in-frame deletion we describe has not previously been reported and adds to our understanding of the biologic effects of p53 gene mutation in Li-Fraumeni syndrome (LFS).

Abstract

Histone deacetylase (HDAC) inhibitors such as the phenyl hydroxamic acid PCI-24781 have emerged recently as a class of therapeutic agents for the treatment of cancer. Recent data showing synergy of HDAC inhibitors with ionizing radiation and other DNA-damaging agents have suggested that HDAC inhibitors may act, in part, by inhibiting DNA repair. Here we present evidence that HDAC enzymes are important for homologous recombinational repair of DNA double-strand breaks. Combination studies of PCI-24781 with the poly(ADP-ribose) polymerase inhibitor PJ34, an agent thought to produce lesions repaired by homologous recombination (HR), resulted in a synergistic effect on apoptosis. Immunofluorescence analysis demonstrated that HDAC inhibition caused a complete inhibition of subnuclear repair foci in response to ionizing radiation. Mechanistic investigations revealed that inhibition of HDAC enzymes by PCI-24781 led to a significant reduction in the transcription of genes specifically associated with HR, including RAD51. RAD51 protein levels were significantly decreased after 24 h of drug exposure both in vitro and in vivo. Consistent with inhibition of HR, treatment with PCI-24781 resulted in a decreased ability to perform homology directed repair of I-SceI-induced chromosome breaks in transfected CHO cells. In addition, an enhancement of cell killing was observed in Ku mutant cells lacking functional nonhomologous end joining compared with WT cells. Together these results demonstrate that HDAC enzymes are critically important to enable functional HR by controlling the expression of HR-related genes and promoting the proper assembly of HR-directed subnuclear foci.

Abstract

High-penetrance autosomal dominant cancer susceptibility genes such as BRCA2 and MEN1 result in specific patterns of cancers in individuals who inherit germline mutations. Their incidence in the population is relatively low, however, and it is highly unusual to identify individuals with two or more inherited cancer gene mutations. We describe a family with multiple cases of MEN1-associated cancers as well as pancreatic adenocarcinoma, ovarian cancer, and male breast cancer, in which we identified germline mutations in both MEN1 and BRCA2. To our knowledge, this is the first report of a patient with both MEN1 and BRCA2 mutations and with a personal history of hyperparathyroidism and pancreatic neuroendocrine tumors.

Abstract

The CDH1 gene encodes the cell adhesion protein E-cadherin, and CDH1 germline mutations are associated with hereditary diffuse gastric cancer. Identification of individuals at high risk of developing diffuse gastric cancer affords the opportunity for endoscopic screening or elective prophylactic gastrectomy. We set out to develop a CDH1 sequencing assay for clinical use.All exons of the CDH1 gene were amplified and sequenced with published and modified primers.While validating the assay, we encountered a case in which a single nucleotide polymorphism located in intron 15 led to allele dropout and therefore to a false-negative result. The polymorphism leading to allele dropout was located within a primer-binding sequence, five bases away from the 3' end of the primer. A frameshift mutation in exon 15 was detected by an alternative primer that binds away from the polymorphic site. A search of the University of California Santa Cruz single nucleotide polymorphism database revealed other polymorphisms located within primer-binding sites. A total of 12 primers in nine primer sets were modified to minimize allele dropout risk.The approach of designing primers to avoid known single nucleotide polymorphisms can be generalized to the design of any polymerase chain reaction-based assay and should be employed whenever possible.

Abstract

Hereditary diffuse gastric cancer is caused by germline mutations in the epithelial cadherin (CDH1) gene and is characterized by an increased risk for diffuse gastric cancer and lobular breast cancer.To determine whether recurring germline CDH1 mutations occurred due to independent mutational events or common ancestry.Thirty-eight families diagnosed clinically with hereditary diffuse gastric cancer were accrued between November 2004 and January 2006 and were analyzed for CDH1 mutations as part of an ongoing study at the British Columbia Cancer Agency. Twenty-six families had at least 2 gastric cancer cases with 1 case of diffuse gastric cancer in a person younger than 50 years; 12 families had either a single case of diffuse gastric cancer diagnosed in a person younger than 35 years or multiple cases of diffuse gastric cancer diagnosed in persons older than 50 years.Classification of family members as carriers or noncarriers of CDH1 mutations. Haplotype analysis to assess recurring mutations for common ancestry was performed on 7 families from this study and 7 previously reported families with the same mutations.Thirteen mutations (6 novel) were identified in 15 of the 38 families (40% detection rate). The 1137G>A splicing mutation and the 1901C>T (A634V) missense/splicing mutation occurred on common haplotypes in 2 families but on different haplotypes in a third family. The 2195G>A (R732Q) missense/splicing mutation occurred in 2 families on different haplotypes. The 2064-2065delTG mutation occurred on a common haplotype in 2 families. Two families from this study plus 2 additional families carrying the novel 2398delC mutation shared a common haplotype, suggesting a founder effect. All 4 families originate from the southeast coast of Newfoundland. Due to concentrations of lobular breast cancer cases, 2 branches of this family had been diagnosed as having hereditary breast cancer and were tested for BRCA mutations. Within these 4 families, the cumulative risk by age 75 years in mutation carriers for clinically detected gastric cancer was 40% (95% confidence interval [CI], 12%-91%) for males and 63% (95% CI, 19%-99%) for females and the risk for breast cancer in female mutation carriers was 52% (95% CI, 29%-94%).Recurrent CDH1 mutations in families with hereditary diffuse gastric cancer are due to both independent mutational events and common ancestry. The presence of a founder mutation from Newfoundland is strongly supported.

Abstract

Our purpose is to describe the appearance of breast ductal enhancement found on magnetic resonance imaging (MRI) after breast ductal lavage (DL). We describe a novel etiology of enhancement in a ductal pattern on postcontrast MRI of the breast. Knowledge of the potential for breast MRI enhancement subsequent to DL, which can mimic the appearance of a pathologic lesion, is critical to the care of patients who undergo breast MRI and DL or other intraductal cannulation procedures.

Abstract

Antimicrotubule agents are commonly used chemotherapy drugs for the treatment of breast and other cancers. However, these agents have variable activity partly because of microtubule regulatory proteins. Stathmin, an 18-kDa phosphoprotein that promotes microtubule depolymerization, was found to be frequently overexpressed in breast cancer. We previously identified stathmin-mediated mechanisms of resistance to antimicrotubule agents, including altered drug binding and delayed transit from G(2) into M phase, where these agents are effective in disrupting microtubule dynamics. We hypothesized that by reversing stathmin-mediated depolymerization of microtubules or by promoting entry into mitosis, this could increase sensitivity to antimicrotubule agents in human breast cancer cells overexpressing stathmin. We found that targeting stathmin or wee-1 expression with RNA interference can induce microtubule polymerization and promote G(2)/M progression, respectively, and sensitize stathmin-overexpressing breast cancer cells to paclitaxel and vinblastine. Furthermore, targeting wee-1 led to the phosphorylation of stathmin, which is known to attenuate its activity. Therefore, these data suggest a novel approach to improving the efficacy of certain antimicrotubule agents against breast cancer by regulating the function of stathmin.

Abstract

The aim of study was to determine the clinical characteristics and mutational profiles of the mismatch repair genes in hereditary nonpolyposis colorectal cancer (HNPCC) patients with small bowel cancer (SBC).A questionnaire was mailed to 55 members of the International Society for Gastrointestinal Hereditary Tumours, requesting information regarding patients with HNPCC-associated SBC and germ line mismatch repair gene mutations.The study population consisted of 85 HNPCC patients with identified mismatch repair gene mutations and SBCs. SBC was the first HNPCC-associated malignancy in 14 of 41 (34.1%) patients for whom a personal history of HNPCC-associated cancers was available. The study population harbored 69 different germ line mismatch repair gene mutations, including 31 mutations in MLH1, 34 in MSH2, 3 in MSH6, and 1 in PMS2. We compared the distribution of the mismatch repair mutations in our study population with that in a control group, including all pathogenic mismatch repair mutations of the International Society for Gastrointestinal Hereditary Tumours database (excluding those in our study population). In patients with MSH2 mutations, patients with HNPCC-associated SBCs had fewer mutations in the MutL homologue interaction domain (2.9% versus 19.9%, P = 0.019) but an increased frequency of mutations in codons 626 to 733, a domain that has not previously been associated with a known function, versus the control group (26.5% versus 2.8%, P < 0.001).In HNPCC patients, SBC can be the first and only cancer and may develop as soon as the early teens. The distribution of MSH2 mutations found in patients with HNPCC-associated SBCs significantly differed from that found in the control group (P < 0.001).

Abstract

Damaged DNA binding proteins (DDBs) play a critical role in the initial recognition of UV-damaged DNA and mediate recruitment of nucleotide excision repair factors. Previous studies identified DDB2 as a target of the CUL-4A ubiquitin ligase. However, the biochemical mechanism governing DDB proteolysis and its underlying physiological function in the removal of UV-induced DNA damage are largely unknown. Here, we report that the c-Abl nonreceptor tyrosine kinase negatively regulates the repair of UV-induced photolesions on genomic DNA. Biochemical studies revealed that c-Abl promotes CUL-4A-mediated DDB ubiquitination and degradation in a manner that does not require its tyrosine kinase activity both under normal growth conditions and following UV irradiation. Moreover, c-Abl activates DDB degradation in part by alleviating the inhibitory effect of CAND1/TIP120A on CUL-4A. These results revealed a kinase-independent function of c-Abl in a ubiquitin-proteolytic pathway that regulates the damage recognition step of nucleotide excision repair.

Abstract

To determine the efficacy of concurrent 5-fluorouracil (5-FU) and intensity-modulated radiotherapy (IMRT) followed by body stereotactic radiosurgery (SRS) in patients with locally advanced pancreatic cancer.In this prospective study, all patients (19) had pathologically confirmed adenocarcinoma and were uniformly staged. Our treatment protocol consisted of 45 Gy IMRT with concurrent 5-FU followed by a 25 Gy SRS boost to the primary tumor.Sixteen patients completed the planned therapy. Two patients experienced Grade 3 toxicity (none had more than Grade 3 toxicity). Fifteen of these 16 patients were free from local progression until death. Median overall survival was 33 weeks.Concurrent IMRT and 5-FU followed by SRS in patients with locally advanced pancreatic cancer results in excellent local control, but does not improve overall survival and is associated with more toxicity than SRS, alone.

Abstract

In response to DNA damage, the p53 tumor suppressor gene product is activated leading to the induction of several downstream cellular processes including cell cycle checkpoints, DNA repair or apoptosis. Experiments first performed in the Hanawalt laboratory identified a p53-dependent pathway affecting global genomic nucleotide excision repair. The mechanisms involved in this process include both transcriptional and post-translational regulation by p53 of the DDB2 and XPC gene products, two critical DNA damage recognition proteins required for GGR. A historical review of this work is presented.

Abstract

Prophylactic mastectomy (PM) is often considered, but variably chosen by women at high inherited risk of breast cancer; few data exist on patient tolerance of intensive breast screening as an alternative to PM. We performed an evaluation of high-risk women's tolerance of a breast screening protocol using clinical breast examination, mammography, breast magnetic resonance imaging (MRI) and ductal lavage (DL), and of change in attitudes toward PM after screening.A questionnaire assessing tolerance of screening procedures and change in opinion towards PM was designed and administered to 43 study participants, after a median follow-up of 13 months. Responses were evaluated according to patient characteristics, including type of study-prompted interventions, BRCA mutation status, and prior history of cancer, via univariate analysis.Most patients [85.3% (68.9-95.1%)] were more opposed or unchanged in their attitudes towards PM after study participation, with only 14.7% (5.0-31.1%) less opposed (P = 0.017) despite a short-interval follow-up MRI rate of 71.7% and a biopsy rate of 37%. Lower rates of maximal discomfort were reported with mammogram [2.8% (0-14.5%)] and MRI [5.6% (0-18.7%)] than with DL [28.6% (14.6-46.3%)], with P = 0.035.Most high-risk women tolerated intensive breast screening well; they were not more inclined towards PM after participating. Future studies should prospectively evaluate larger numbers of high-risk women via multivariate analysis, to determine characteristics associated with preference for breast screening vs. PM.

Abstract

To investigate the gefitinib, fluorouracil (FU), leucovorin, and oxaliplatin regimen (IFOX) in previously treated patients with metastatic colorectal cancer.Eligible patients had stage IV colorectal adenocarcinoma and had demonstrated progression or intolerance to a prior chemotherapy regimen not including oxaliplatin. Each cycle consisted of 14 days. Cycle 1 consisted of oxaliplatin 85 mg/m2 intravenously (IV) during 2 hours on day 1, hours 0 to 2; leucovorin 200 mg/m2 IV on days 1 and 2, hours 0 to 2; FU 400 mg/m2 IV push on days 1 and 2; and FU 600 mg/m2 IV on days 1 and 2, hours 2 to 24 (FOLFOX-4). All subsequent cycles consisted of FOLFOX-4 with gefitinib at 500 mg/d administered orally throughout the 14-day cycle.Twenty-seven patients were enrolled onto the study. The median number of prior chemotherapy regimens was two, and 74% of all patients received prior irinotecan. Nine of the 27 patients (33%) and six of the 20 patients (30%) who had prior FU and irinotecan had a partial response by Response Evaluation Criteria in Solid Tumors Group criteria. Median overall survival was 12.0 months. Median event-free survival was 5.4 months. Grade 3 to 4 toxicities included neutropenia (48%), diarrhea (48%), nausea (22%), and vomiting (15%).IFOX is an active regimen in patients with previously treated metastatic colorectal adenocarcinoma, demonstrating higher response rates than those reported with FOLFOX-4 alone in a similar patient population.

Abstract

To identify germ line CDH1 mutations in hereditary diffuse gastric cancer (HDGC) families and develop guidelines for management of at risk individuals.We ascertained 31 HDGC previously unreported families, including 10 isolated early-onset diffuse gastric cancer (DGC) cases. Screening for CDH1 germ line mutations was done by denaturing high-performance liquid chromatography and automated DNA sequencing.We identified eight inactivating and one missense CDH1 germ line mutation. The missense mutation conferred in vitro loss of protein function. Two families had the previously described 1003C>T nonsense mutation. Haplotype analysis revealed this to be a recurrent and not a founder mutation. Thirty-six percent (5 of 14) of the families with a documented DGC diagnosed before the age of 50 and other cases of gastric cancer carried CDH1 germ line mutations. Two of 10 isolated cases of DGC in individuals ages <35 years harbored CDH1 germ line mutations. One mutation positive family was ascertained through a family history of lobular breast cancer (LBC) and another through an individual with both DGC and LBC. Occult DGC was identified in five of six prophylactic gastrectomies done on asymptomatic, endoscopically negative 1003C>T mutation carriers.In addition to families with a strong history of early-onset DGC, CDH1 mutation screening should be offered to isolated cases of DGC in individuals ages <35 years and for families with multiple cases of LBC, with any history of DGC or unspecified GI malignancies. Prophylactic gastrectomy is potentially a lifesaving procedure and clinical breast screening is recommended for asymptomatic mutation carriers.

Abstract

Nipple fluid production and atypical breast duct cells in women at high risk of breast cancer have been associated with further increased risk. Most publications on ductal lavage for cell collection report cannulating fluid-yielding ducts only. We report lavage of fluid-yielding and non-fluid-yielding ducts in women at high inherited breast cancer risk.A pilot breast cancer screening study including ductal lavage was conducted in 75 women at high inherited risk, 56 (74.7%) of whom had BRCA1/2 mutations. Ductal lavage was attempted in any duct identifiable with a catheter.Ducts were successfully catheterized in 60 of 75 patients (80%). Successfully catheterized patients were younger (median age 41 versus 53 years, P = 0.0003) and more often premenopausal (51.7% versus 20%, P = 0.041). Thirty-one successfully catheterized patients [51.6%, 95% confidence interval (39.4-63.9%)] had non-fluid-yielding ducts only. Seventeen patients [28.3% (18.5-40.9%)] had atypical cells. Twelve of seventeen [70.6% (46.8-87.2%)] samples with atypia were from non-fluid-yielding ducts. Patients with non-fluid-yielding ducts (versus fluid-yielding ducts) were more likely to have had prior cancer (48.4% versus 17.2%, P = 0.014) or chemotherapy (45.2% versus 17.2%, P = 0.027); this was also true in patients with atypia from non-fluid-yielding ducts.Successfully lavaged women were younger and more often premenopausal. Atypical cells can be found in non-fluid-yielding ducts in patients at high inherited breast cancer risk. Non-fluid-yielding ducts, and atypia from non-fluid-yielding ducts, are more common in patients with prior cancer and chemotherapy. Larger studies are needed to identify risk factors and prognostic significance associated with atypia and non-fluid-yielding ducts in high-risk populations, and define their role as biomarkers.

Abstract

To determine the feasibility and toxicity of delivering stereotactic radiosurgery to patients with locally advanced pancreatic cancer.Patients with Eastern Cooperative Oncology Group performance status < or=2 and locally advanced pancreatic cancer were enrolled on this Phase I dose escalation study. Patients received a single fraction of radiosurgery consisting of either 15 Gy, 20 Gy, or 25 Gy to the primary tumor. Acute gastrointestinal toxicity was scored according to the Radiation Therapy Oncology Group criteria. Response to treatment was determined by serial high-resolution computed tomography scanning.Fifteen patients were treated at 3 dose levels (3 patients received 15 Gy, 5 patients received 20 Gy, and 7 patients received 25 Gy). At these doses, no Grade 3 or higher acute gastrointestinal toxicity was observed. This trial was stopped before any dose-limiting toxicity was reached, because the clinical objective of local control was achieved in all 6 evaluable patients treated at 25 Gy.It is feasible to deliver stereotactic radiosurgery to patients with locally advanced pancreatic cancer. The recommended dose to achieve local control without significant acute gastrointestinal toxicity is 25 Gy.

Abstract

Intensive screening is an alternative to prophylactic mastectomy in women at high risk for developing breast carcinoma. The current article reports preliminary results from a screening protocol using high-quality magnetic resonance imaging (MRI), ductal lavage (DL), clinical breast examination, and mammography to identify early malignancy and high-risk lesions in women at increased genetic risk of breast carcinoma.Women with inherited BRCA1 or BRCA2 mutations or women with a >10% risk of developing breast carcinoma at 10 years, as estimated by the Claus model, were eligible. Patients were accrued from September 2001 to May 2003. Enrolled patients underwent biannual clinical breast examinations and annual mammography, breast MRI, and DL.Forty-one women underwent an initial screen. Fifteen of 41 enrolled women (36.6%) either had undergone previous bilateral oophorectomy and/or were on tamoxifen at the time of the initial screen. One patient who was a BRCA1 carrier had high-grade ductal carcinoma in situ (DCIS) that was screen detected by MRI but that was missed on mammography. High-risk lesions that were screen detected by MRI in three women included radial scars and atypical lobular hyperplasia. DL detected seven women with cellular atypia, including one woman who had a normal MRI and mammogram.Breast MRI identified high-grade DCIS and high-risk lesions that were missed by mammography. DL detected cytologic atypia in a high-risk cohort. A larger screening trial is needed to determine which subgroups of high-risk women will benefit and whether the identification of malignant and high-risk lesions at an early stage will impact breast carcinoma incidence and mortality.

Abstract

The most versatile cellular pathway for dealing with a large variety of structurally-unrelated DNA alterations is nucleotide excision repair (NER). Most genomic damage, if not repaired, may contribute to mutagenesis and carcinogenesis, as well as to cellular lethality. There are two subpathways of NER, termed global genomic repair (GGR) and transcription-coupled repair (TCR); While GGR deals with all repairable lesions throughout the genome, TCR is selective for the transcribed DNA strand in expressed genes. Proteins involved in the initial recognition of lesions for GGR as well as for TCR (i.e. RNA polymerase) may sometimes initiate gratuitous repair events in undamaged DNA. However, the damage recognition enzymes for GGR are normally maintained at very low levels unless the cells are genomically stressed. Following UV irradiation in human fibroblasts the efficiency of GGR is upregulated through activation of the p53 tumor suppressor gene. The transactivation role of p53 includes control of expression of the genes, XPC and XPE, which are implicated in GGR but not TCR. These inducible responses are essential for the efficient repair of the most prominent lesion produced by UV, the cyclobutane pyrimidine dimer (CPD). They are also clinically relevant, as we have shown them to operate upon chemical carcinogen DNA damage at levels to which humans are environmentally exposed (e.g. through smoking). Thus, for benzo(a)pyrene (at 10-50 adducts per 10(8) nucleotides) repair was essentially complete within 1 day in p53(+/+) human fibroblasts while no repair was detected within 3 days in p53(-/-) cells. The levels of all four DNA adducts formed by benzo(g)chrysene, also exhibited p53-dependent control in human fibroblasts. However, unlike humans most rodent tissues are deficient in the p53-dependent GGR pathway. Since rodents are used as surrogates for humans in environmental cancer risk assessment it is very important that we determine how they differ from humans with respect to DNA repair and oncogenic responses to environmental genotoxins.

Abstract

The BRCA1 breast cancer susceptibility gene has been implicated in many cellular processes, yet its specific mechanism of tumor suppression remains unclear. BRCA1 plays a role in several DNA repair pathways including nucleotide excision repair (NER). Loss of the p53 tumor suppressor gene, a key regulator of NER, is an important and necessary event in the pathogenesis of BRCA1-mutated tumors. Here we discuss the role of BRCA1 and NER in breast cancer and the interactions of BRCA1 with p53 in breast tumorigenesis and suggest approaches for risk assessment and chemotherapeutic management of BRCA1-related breast cancer.

Abstract

DNA repair mechanisms are essential for the maintenance of genomic integrity. Disruption of gene products responsible for DNA repair can result in chromosomal damage. Improperly repaired chromosomal damage can result in the loss of chromosomes or the generation of chromosomal deletions or translocations, which can lead to tumorigenesis. The MYC protooncogene is a transcription factor whose overexpression is frequently associated with human neoplasia. MYC has not been previously implicated in a role in DNA repair. Here we report that the overexpression of MYC disrupts the repair of double-strand DNA breaks, resulting in a several-magnitude increase in chromosomal breaks and translocations. We found that MYC inhibited the repair of gamma irradiation DNA breaks in normal human cells and blocked the repair of a single double-strand break engineered to occur in an immortal cell line. By spectral karyotypic analysis, we found that MYC even within one cell division cycle resulted in a several-magnitude increase in the frequency of chromosomal breaks and translocations in normal human cells. Hence, MYC overexpression may be a previously undescribed example of a dominant mutator that may fuel tumorigenesis by inducing chromosomal damage.

Abstract

The p53 tumor suppressor gene is a transcriptional activator involved in cell cycle regulation, apoptosis, and DNA repair. We have shown that p53 is required for efficient nucleotide excision repair of UV-induced DNA photoproducts from global genomic DNA but has no effect on transcription-coupled repair. In order to evaluate whether p53 influences repair indirectly through cell cycle arrest following DNA damage or plays a direct role, we examined repair in vivo in human cells genetically altered to disrupt or regulate the function of p53 and p21. Both primary human fibroblasts and HCT116 colon carcinoma cells wild type for p53 but in which the p21 gene was inactivated through targeted homologous recombination showed no decrease in global repair of UV photoproducts. Human bladder carcinoma cells mutant for p53 and containing a tetracycline-regulated p21 cDNA showed no significant enhancement of repair upon induction of p21 expression. All of the cell lines, including the mismatch repair-deficient, MLH1 mutant HCT116 cells, were proficient for transcription-coupled repair. Clonogenic survival of HCT116 cells following UV irradiation showed no dependence on p21. Therefore, our results indicate that p53-dependent nucleotide excision repair does not require the function of the p21 gene product and is independent of p53-regulated cell cycle checkpoints.

Abstract

Radiation therapy (RT) with concurrent 5-fluorouracil (5-FU) administered by protracted venous infusion (PVI) replaced our prior institutional protocol of RT with bolus administration of 5-FU as standard therapy for unresectable pancreatic cancer in 1994. In this article, we compare the treatment intensity, toxicity, and outcome for patients with unresectable pancreatic cancer treated on these sequential protocols. Fifty-four patients, 27 on each protocol, with biopsy-confirmed pancreatic cancer received chemoradiotherapy. The radiotherapy field included the gross tumor volume and regional lymph nodes to a dose of 45 Gy, followed by "boost" to the gross tumor volume to 54 Gy to 60 Gy. From 1987 to 1994, patients received concurrent 5-FU administered by bolus injection, at a dose of 500 mg/m2 on days 1 to 3 and days 29 to 31 of RT. After December 1994, 5-FU was administered by PVI (200-250 mg/m2) beginning on day 1 and continuing until the completion of RT. The chemotherapy treatment intensity was increased in the group receiving 5-FU by PVI, as evidenced by an increased average weekly and cumulative dose of 5-FU (p < 0.01). The radiotherapy treatment intensity was equivalent between the two groups. The incidence of objectively quantified toxicity was not statistically different between treatment groups. Overall survival remained poor in both treatment groups. With a median follow-up of 18 months (range: 3-30 months) for surviving patients, the 6-month, 1-year, and 2-year survivals for the PVI 5-FU-treated group versus the bolus 5-FU-treated group were 56% versus 52%, 34% versus 18%, and 22% versus 13%, respectively (p = 0.9). Radiotherapy with concomitant 5-FU by PVI results in a greater weekly and total dose of chemotherapy. The method of 5-FU administration (bolus versus PVI) did not change the RT treatment intensity, experienced toxicity, or overall survival.

Abstract

A prospective study was undertaken to evaluate the response and toxicity of neoadjuvant chemoradiotherapy for ultrasound-staged T3 or T4 rectal cancer.Since 1995, 30 patients (18 males; median age, 56 (range, 25-83) years) have received preoperative chemoradiotherapy for ultrasound-staged T3 or T4 rectal cancer. All patients underwent an endorectal ultrasound, CT scan, and review in our multidisciplinary Gastrointestinal Tumor Board before treatment. All patients had pathology-demonstrated invasive adenocarcinoma of the rectum. Eleven patients were Stage T3N0, 14 were T3N1, and five were T4N1. Patients received radiotherapy to the primary tumor and draining lymph nodes (45 Gy) followed by a tumor boost (50.4-54 Gy). Protracted-venous-infusion 5-fluorouracil (225 mg/m2 per day, seven days per week) was administered throughout treatment. Surgical resection was performed six to ten weeks after completing chemoradiotherapy. Using endorectal ultrasound measurements, the primary tumor was a median of 4 (range, 0-12) cm from the anal verge, encompassed 50 (range, 20-90) percent of the rectal circumference, and was 6 (range, 3-12) cm in diameter.No Grade 4 toxicity was observed during chemoradiotherapy. Three patients experienced Grade 3 toxicity (diarrhea), and four patients required a treatment interruption of greater than three days. All patients completed at least 90 percent of the prescribed radiotherapy dose. All patients underwent surgical resection. Ninety-four percent had clear surgical margins. All pathologic specimens had significant evidence of necrosis, hyalinization, and fibrosis. Thirty-three percent of the specimens had a complete pathologic response (defined as no evidence of viable tumor cells). Of the 19 patients with ultrasound-staged N1 disease, only five had pathologic evidence of nodal involvement after chemoradiotherapy. Of the 25 patients with ultrasound-staged T3 disease, pathologic staging revealed eight with T0, two with T1, five with T2, and ten with T3 disease. Of the five patients with ultrasound-staged T4 disease, pathologic staging revealed two with T0, one with T2, and two with T3 disease. No patient developed progressive disease while on treatment. Two patients have experienced local failure at 6 and 20 months, and one patient failed in the liver at seven months. Twenty-seven patients remain free of disease with a median follow-up of 20 (range, 3-53) months.Our experience suggests that preoperative chemoradiotherapy is well tolerated, down-stages tumors, and sterilizes regional lymph nodes.

Abstract

Only 10% to 20% of patients with pancreatic cancer are considered candidates for curative resection at the time of diagnosis. We postulated that preoperative chemoradiation therapy might promote tumor regression, eradicate nodal metastases, and allow for definitive surgical resection in marginally resectable patients. The objective of this study was to evaluate the effect of a preoperative chemoradiation therapy regimen on tumor response, resectability, and local control among patients with marginally resectable adenocarcinoma of the pancreas and to report potential treatment-related toxicity. Patients with marginally resectable adenocarcinoma of the pancreas (defined as portal vein, superior mesenteric vein, or artery involvement) were eligible for this protocol. Patients received 50.4 to 56 Gy in 1.8 to 2.0 Gy/day fractions with concurrent protracted venous infusion of 5-fluorouracil (250 mg/m2/day). Reevaluation for surgical resection occurred 4 to 6 weeks after therapy. Fifteen patients (9 men and 6 women) completed preoperative chemoradiation without interruption. One patient required a reduction in the dosage of 5-fluorouracil because of stomatitis. Acute toxicity from chemoradiation consisted of grade 1 or 2 nausea, vomiting, diarrhea, stomatitis, palmar and plantar erythrodysesthesia, and hematologic suppression. CA 19-9 levels declined in all nine of the patients with elevated pretreatment levels. Nine of the 15 patients underwent a pancreaticoduodenectomy, and all had uninvolved surgical margins. Two of these patients had a complete pathologic response, and two had microscopic involvement of a single lymph node. With a median follow-up of 30 months, the median survival for resected patients was 30 months, whereas in the unresected group median survival was 8 months. Six of the nine patients who underwent resection remain alive and disease free with follow-up of 12, 30, 30, 34, 39, and 72 months, respectively. Preoperative chemoradiation therapy is well tolerated. It may downstage tumors, sterilize regional lymph nodes, and improve resectability in patients with marginally resectable pancreatic cancer. Greater patient accrual and longer follow-up are needed to more accurately assess its future role in therapy.

Abstract

Adjuvant chemoradiotherapy decreases the risk of local recurrence in patients with adenocarcinoma of the ampulla of Vater and high-risk features. Adjuvant chemoradiotherapy for this population can be administered safely and without much morbidity.Controlled, prospective, single-arm study.Tertiary care referral hospital.From June 1995 to March 1999, 12 patients (7 men and 5 women; median age, 66 years; age range, 38-78 years) with "unfavorable" ampullary carcinoma were treated with adjuvant chemoradiotherapy. All patients underwent pancreaticoduodenectomy, and all pathologic findings were confirmed at Stanford University Medical Center, Stanford, Calif. Unfavorable features were defined as involved lymph nodes (n = 10), involved surgical margins (n = 1), poorly differentiated histological features (n = 3), tumor size greater than 2 cm (n = 6), or the presence of neurovascular invasion (n = 4).Four to 6 weeks after undergoing pylorus-preserving pancreaticoduodenectomy with regional lymphadenectomy, patients began adjuvant chemoradiotherapy consisting of concurrent radiotherapy (45 Gy) and fluorouracil by protracted venous infusion (225-250 mg/m(2) per day, 7 days per week) for 5 weeks.Local recurrence, distant recurrence, overall survival rate, and treatment-related toxic effects.All patients completed the prescribed treatment course. Toxic effects were assessed twice a week during treatment and graded according to the National Cancer Institute Common Toxicity Criteria Scale. One patient required a treatment interruption of 1 week for grade III nausea/vomiting. No grade IV or V toxic effects were observed. At median follow-up of 24 months (range, 13-50 months), 8 of 12 patients were alive and disease free. One patient was alive but had disease recurrence. Three patients died of this disease (liver metastases). Actuarial overall survival at 2 years was 89%, and median survival was 34 months. One surviving patient developed a local recurrence and a lung lesion. Actuarial overall survival and median survival were better than in a parallel cohort with resected high-risk pancreatic cancer (n = 26) treated with the same adjuvant chemoradiotherapy regimen (median survival, 34 vs 14 months; P

Abstract

To assess the toxicity and clinical benefit from adjuvant chemoradiotherapy consisting of protracted venous infusion 5-fluorouracil (5-FU) and concomitant radiotherapy in patients with resected pancreatic cancer.Between 1994 and 1999, 52 patients who underwent pancreaticoduodenectomy received adjuvant chemoradiotherapy. The tumor bed and regional nodes received a dose of 45 Gy in fractions of 1.8 Gy followed by boost to the tumor bed if the surgical margins were involved (total dose, 54 Gy). The patients also received concomitant 5-FU by protracted venous infusion (200-250 mg/m(2)/day, 7 days/week) during the entire radiotherapy course.Fifty-two patients (30 men, 22 women) were enrolled and treated on this protocol. The median age was 63 years (range, 38-78 years), and the median Karnofsky Performance Status was 80 (range, 70-100). Thirty-five percent had involved surgical margins and 59% had involved lymph nodes. All patients completed therapy, and there were no Grade IV/V toxicities observed. With median follow-up of 24 months (range, 3-52 months) for surviving patients, the median survival is 32 months, and 2-year and 3-year survivals are 62%, and 39%, respectively.Radiotherapy with concomitant 5-FU by protracted venous infusion as adjuvant treatment for resected pancreatic cancer is well tolerated. This approach allows for greater dose intensity with reduced toxicity. The median survival of this cohort of patients compares favorably with our earlier experience and other published series.

Abstract

p53 is an important mediator of the cellular stress response with roles in cell cycle control, DNA repair, and apoptosis. 53BP2, a p53-interacting protein, enhances p53 transactivation, impedes cell cycle progression, and promotes apoptosis through unknown mechanisms. We now demonstrate that endogenous 53BP2 levels increase following UV irradiation induced DNA damage in a p53-independent manner. In contrast, we found that the presence of a wild-type (but not mutant) p53 gene suppressed 53BP2 steady-state levels in cell lines with defined p53 genotypes. Likewise, expression of a tetracycline-regulated wild-type p53 cDNA in p53-null fibroblasts caused a reduction in 53BP2 protein levels. However, 53BP2 levels were not reduced if the tetracycline-regulated p53 cDNA was expressed after UV damage in these cells. This suggests that UV damage activates cellular factors that can relieve the p53-mediated suppression of 53BP2 protein. To address the physiologic significance of 53BP2 induction, we utilized stable cell lines with a ponasterone A-regulated 53BP2 cDNA. Conditional expression of 53BP2 cDNA lowered the apoptotic threshold and decreased clonogenic survival following UV irradiation. Conversely, attenuation of endogenous 53BP2 induction with an antisense oligonucleotide resulted in enhanced clonogenic survival following UV irradiation. These results demonstrate that 53BP2 is a DNA damage-inducible protein that promotes DNA damage-induced apoptosis. Furthermore, 53BP2 expression is highly regulated and involves both p53-dependent and p53-independent mechanisms. Our data provide new insight into 53BP2 function and open new avenues for investigation into the cellular response to genotoxic stress.

Abstract

The p53 tumor-suppressor gene has been implicated in the inducible activation of excision repair of ultraviolet (UV)-induced cyclobutane pyrimidine dimers (CPDs) in human cells. Because the large T antigen (LTAg) of the simian virus 40 (SV40) binds p53 protein and can interfere with its function, it was of interest to study DNA repair in normal human fibroblasts that had been transformed by SV40 compared with that in their nontransformed parental counterparts and to determine whether such transformation attenuated global genomic repair (GGR) of CPDs. Three methods were used to measure GGR in UV-irradiated cells: (i) an immunoassay using monoclonal antibodies specific for CPDs or 6-4 photoproducts (6-4PPs), (ii) zone sedimentation in alkaline sucrose gradients to measure the average DNA strand size after specific nicking at CPD sites in duplex DNA with T4 endonuclease V (TEV), and (iii) Southern hybridization of TEV-treated DNA with strand-specific mRNA probes to assess removal of CPDs from either strand of a defined genetic sequence in an expressed gene. Whereas repair of 6-4PPs was very similar in paired SV40-transformed and primary fibroblasts, GGR of CPDs was significantly reduced in the SV40-transformed cells. In contrast, SV40 transformation did not appreciably affect the efficiency of transcription-coupled repair. These data support the hypothesis that SV40 transformation can result in reduced levels of GGR, most likely because of the inhibition of normal p53 function by LTAg.

Abstract

Xeroderma pigmentosum group A gene (XPA)-deficient mice are defective in nucleotide excision repair (NER) and are therefore highly sensitive to ultraviolet (UV)-induced skin carcinogenesis. We established cell lines from skin cancers of UVB-irradiated XPA-deficient mice to investigate the phenotypic changes occurring during skin carcinogenesis. As anticipated, the skin cancer cell lines were devoid of NER activity but were less sensitive to killing by UV-irradiation than the XPA(-/-) fibroblast cell line. The lines were also more resistant to 6-thioguanine (6-TG) than XPA(-/-) and XPA(+/+) fibroblasts, which was suggestive of a mismatch repair (MMR) defect. Indeed, in vitro mismatch binding and MMR activity were impaired in several of these cell lines. Moreover, these cell lines displayed cell cycle checkpoint derangements following UV-irradiation and 6-TG exposure. The above findings suggest that MMR downregulation may help cells escape killing by UVB, as was seen previously for methylating agents and cisplatin, and thus that MMR deficient clones are selected for during the tumorigenic transformation of XPA(-/-) cells.

Abstract

Human cells lacking functional p53 exhibit a partial deficiency in nucleotide excision repair (NER), the pathway for repair of UV-induced DNA damage. The global genomic repair (GGR) subpathway of NER, but not transcription-coupled repair (TCR), is mainly affected by p53 loss or inactivation. We have utilized mouse embryo fibroblasts (MEFs) lacking p53 genes or downstream effector genes of the p53 pathway, gadd45 (Gadd45a) or p21 (Cdkn1a), as well as MEFs lacking both gadd45 and p21 genes to address the potential contribution of these downstream effectors to p53-associated DNA repair. Loss of p53 or gadd45 had a pronounced effect on GGR, while p21 loss had only a marginal effect, determined by measurements of repair synthesis (unscheduled DNA synthesis), by immunoassays to detect removal of UV photoproducts from genomic DNA, and by assays determining strand-specific removal of CPDs from the mouse dhfr gene. Taken together, the evidence suggests a role for Gadd45, but relatively little role for p21, in DNA repair responses to UV radiation. Recent evidence suggests that Gadd45 binds to UV-damaged chromatin and may affect lesion accessibility. MEFs lacking p53 or gadd45 genes exhibited decreased colony-forming ability after UV radiation and cisplatin compared to wild-type MEFs, indicating their sensitivity to DNA damage. We provide evidence that Gadd45 affects chromatin remodelling of templates concurrent with DNA repair, thus indicating that Gadd45 may participate in the coupling between chromatin assembly and DNA repair.

Abstract

In western countries, carcinoma of the pancreas remains the most lethal of the common malignancies. Even the favorable "organ-confined" tumors present a considerable challenge. The lack of anatomic barriers to local infiltration and the biological propensity for early lymphatic, perineural, and vascular invasion are nearly insurmountable obstacles to complete surgical eradication of this malignancy. Various combinations of chemotherapy and radiotherapy (RT) have been used with marginal but measurable success. Earlier trials conducted by the Gastrointestinal Tumor Study Group established roles for 5-fluorouracil chemotherapy and RT in the treatment of patients with resectable or locally advanced pancreatic cancer. More recently, computed tomography-guided conformal RT and a variety of intraoperative RT techniques have enabled more reliable sterilization of the local surgical field and escalation of doses to potentially curative levels (7000 cGy) for unresectable lesions. Chemotherapy dose intensification through the use of portable programmable pumps for protracted venous infusions and the development of active systemic agents in addition to 5-fluorouracil suggest that an effective combination chemotherapeutic regimen might soon be developed. This report reviews the current standards of practice and integrates recent developments to construct a modern algorithm for the use of chemoradiotherapy in the management of localized (nonmetastatic) pancreatic cancer. The likely directions of future investigations are also discussed.

Abstract

The mechanisms by which the hepatitis B x protein (HBx) contributes to hepatocarcinogenesis remain unclear. However, interaction with the tumor suppressor gene p53 and inhibition of p53-dependent cellular functions, including nucleotide excision repair, could be central to this process. We studied the levels of global repair (removal of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts) and transcription-coupled repair (removal of CPDs in both strands of the dihydrofolate reductase gene) in primary wild-type and p53-null mouse hepatocytes. We show that global repair of CPDs appears to be more efficient in mouse hepatocytes than in other commonly studied rodent cells and approaches the levels of human cells and that p53 is required for global genomic DNA repair of CPDs but not for transcription-coupled repair. We then investigated the effect of HBx expression on hepatocyte nucleotide excision repair. We demonstrate that HBx expression affects DNA repair in a p53-dependent manner. Transient HBx expression reduces global DNA repair in wild-type cells to the level of p53-null hepatocytes and has no effect on the repair of a transfected damaged plasmid. Therefore, in viral hepatitis, the hepatitis B virus could inhibit the p53-dependent component of global repair leading, over time, to accumulation of genetic defects and fostering carcinogenesis.

Abstract

We investigated the role of wild-type p53 activity in modulating nucleotide excision repair after UV irradiation in normal and p53-deficient primary human fibroblasts created by expression of the human papillomavirus 16 E6 gene. Compared with parental cells, the E6-expressing fibroblasts were deficient in global genomic repair of both UV-induced cyclobutane pyrimidine dimers and 6-4 photoproducts but exhibited normal transcription-coupled repair. The E6-expressing cells were also more sensitive than their parental counterparts to UV irradiation and displayed similar levels of UV-induced apoptosis. These results suggest that disruption of wild-type p53 function by E6 expression results in selective loss of p53-dependent global genomic nucleotide excision repair, but not UV-induced apoptosis, leading to enhanced UV sensitivity.

Abstract

The study of the cellular, biochemical, and molecular biology and pharmacology of MDR has provided one of the most active and exciting areas within cancer research and one that holds great promise for translation into clinical benefit. While convincing evidence for the functional role of P-gp in mediating clinical drug resistance in humans remains elusive, studies of the clinical expression of P-gp and trials of chemosensitizers with cancer chemotherapy suggest "resistance modification" strategies may be effective in some tumors with intrinsic or acquired drug resistance. However, even if P-gp-associated MDR proves to be a relevant and reversible cause of clinical drug resistance, numerous problems remain to be solved before effective clinical chemosensitization may be achieved. Such factors as absorption, distribution, and metabolism; the effect of chemosensitizers on chemotherapeutic drug clearance; toxicity to normal tissues expressing P-gp; and the most efficacious modulator regimens all remain to be defined in vivo. Clearly, the identification of more specific, potent, and less clinically toxic chemosensitizers for clinical use remains critical to the possible success of this approach. Nonetheless, the finding that a number of pharmacological agents can antagonize a well-characterized form of experimental drug resistance provides promise for potential clinical applications. Further study of chemosensitizers in humans and the rational design of novel chemosensitizers with improved activity should define the importance of MDR in clinically resistant cancer.

Abstract

The study of the cellular, biochemical, and molecular biology and pharmacology of MDR has provided one of the most active and exciting areas within cancer research for translation into potential clinical benefit. Although convincing evidence for the functional role of P-gp in mediating clinical drug resistance in humans remains scant, studies of the clinical expression of P-gp and trials of chemosensitizers with cancer chemotherapy suggest "resistance modification" strategies may be effective in some tumors with intrinsic or acquired drug resistance. However, even if P-gp-associated MDR proves to be a relevant and reversible cause of clinical drug resistance, numerous problems remain to be solved before effective clinical chemosensitization may be achieved. Such factors as absorption, distribution, and metabolism, the effect of chemosensitizers on chemotherapeutic drug clearance, toxicity to normal tissues expressing P-gp, and the most efficacious modulator regimens all remain to be defined in vivo. Clearly, the identification of more specific, more potent, and less clinically toxic chemosensitizers for clinical use remains critical to the possible success of this approach. However, the finding that a number of pharmacologic agents can antagonize a well-characterized form of experimental drug resistance provides promise for potential clinical applications. Further study of chemosensitizers in humans and the rational design of novel chemosensitizers with improved activity should define the importance of MDR to clinically resistant cancer.

Abstract

Mutations in the p53 tumor suppressor gene have been found in most human tumors. Analyses of the spectrum of p53 mutations in certain tumor types have shown a bias for mutations originating from lesions presumed to be in the untranscribed strand of the gene. This implies strand specificity for the formation or repair of DNA damage. We measured the induction and repair of ultraviolet light-induced cyclobutane pyrimidine dimers (CPD) in each strand of the human p53 gene in a normal human lung fibroblast cell line using quantitative Southern hybridization. We found that the removal of CPD from the transcribed strand was more rapid than that from the untranscribed strand of this gene, although the frequency of CPD induction was similar in both strands. Preferential repair of the transcribed strand of the p53 gene may account for the mutational spectra of this gene in human tumors.

Abstract

The ability of malignant cells to develop resistance to chemotherapeutic drugs is a major obstacle to the successful treatment of clinical tumors. The phenomenon multidrug resistance (MDR) in cancer cells results in cross-resistance to a broad range of structurally diverse antineoplastic agents, due to outward efflux of cytotoxic substrates by the mdr1 gene product, P-glycoprotein (P-gp). Numerous pharmacologic agents have been identified which inhibit the efflux pump and modulate MDR. The biochemical, cellular and clinical pharmacology of agents used to circumvent MDR is analyzed in terms of their mechanism of action and potential clinical utility. MDR antagonists, termed chemosensitizers, may be grouped into several classes, and include calcium channel blockers, calmodulin antagonists, anthracycline and Vinca alkaloid analogs, cyclosporines, dipyridamole, and other hydrophobic, cationic compounds. Structural features important for chemosensitizer activity have been identified, and a model for the interaction of these drugs with P-gp is proposed. Other possible cellular targets for the reversal of MDR are also discussed, such as protein kinase C. Strategies for the clinical modulation of MDR and trials combining chemosensitizers with chemotherapeutic drugs in humans are reviewed. Several novel approaches for the modulation of MDR are examined.

Abstract

Resistance of tumor cells to chemotherapeutic drugs may be due to several mechanisms within a single cell line. Resistance to doxorubicin in the human multidrug resistant breast cancer cell line, MCF-7 AdrR, has been attributed to increased glutathione (GSH) S-transferase and GSH peroxidase activity, as well as to increased expression of the mdr1 gene product, P-glycoprotein. We studied the potentiation of doxorubicin activity in these cells by buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine synthetase, and by verapamil and trans-flupenthixol, agents which interact with P-glycoprotein. Treatment with BSO enhanced the effect of doxorubicin by 1.5-fold, while verapamil or transflupenthixol caused a greater reversal of drug resistance. The combination of BSO with trans-flupenthixol produced no further potentiation of doxorubicin activity. However, the combination of BSO with verapamil and doxorubicin caused up to a 10-fold increment in antiproliferative effect. To explore the mechanism by which BSO interacted with this drug combination, we determined whether or not BSO might potentiate the effects of verapamil. These studies demonstrated that the effects of BSO were predominantly due to an increase in verapamil toxicity rather than to doxorubicin toxicity. In addition, when mice received concentrations of BSO in their drinking water sufficient to deplete GSH and were treated with verapamil, the calcium channel blocker was lethal to 9 of 12 mice receiving BSO compared to 1 of 10 control animals receiving verapamil alone. These studies demonstrate that BSO does not markedly increase the pharmacological effect of doxorubicin against MCF-7 AdrR cells and suggest that alterations in GSH and related enzymes are not a major factor in drug resistance in this cell line. Furthermore, BSO can increase the toxicity of verapamil, a finding which may have important implications for clinical trials.

Abstract

Several cell lines resistant to alkylating agents possess increased activity of glutathione-S-transferase (GST) drug detoxifying enzymes. Inhibition of certain enzymes of the glutathione redox system may affect cellular sensitivity to alkylators. We report that the (-.)enantiomer of gossypol is a potent and selective inhibitor of GST alpha and GST pi isozymes, and that in combination with buthionine sulfoximine (BSO), causes the enhanced modulation of alkylator resistance in two drug resistant cell lines with increased GST activity. The use of (-)gossypol alone had no effect on the 2-5-fold resistance of MCF-7 Adr and Walker resistant cells to chlorambucil, melphalan and BCNU. Cellular depletion of glutathione with BSO resulted in a 2-4-fold modulation of cell sensitivity to these alkylators. However, the combination of (-)gossypol with BSO resulted in a markedly greater modulation of alkylator sensitivity than with either inhibitor alone. Therefore, the complementary inhibition of glutathione and GST by BSO and (-)gossypol, respectively, produced a synergistic modulation of alkylator cytotoxicity in these drug resistant cell lines. The favorable clinical pharmacokinetics of (-)gossypol suggest its further evaluation for use in combination with BSO and alkylating agents in clinical trials.

Abstract

Racemic gossypol has been shown to have antitumor properties that may be due to its ability to uncouple tumor mitochondria or to its inhibitory effects on a variety of nonmitochondrial enzymes. We have studied the antimitochondrial and enzyme-inhibiting properties of gossypol in human carcinoma cell lines of breast (MCF-7, T47-D), ovarian (OVCAR-3) colon (HCT-8), and pancreatic (MiaPaCa) origin by comparing the effects of its purified (+)- and (-)-enantiomers. (-)-Gossypol shows up to 10-fold greater antiproliferative activity than (+)-gossypol in the cancer cell lines and in normal hematopoietic stem cells grown in vitro, with IC50 values ranging from 1.5 to 4.0 microM for the cancer cells and from 10 to 20 microM for the human marrow stem cells. As well, multidrug-resistant MCF/Adr cells appear more resistant to (-)-gossypol than their parental cell line. Electron microscopy indicates that the earliest ultrastructural change in tumor cells exposed to a cytotoxic (10 microM) concentration of (-)-gossypol is the selective destruction of their mitochondria. Consistent with this observation, 31P magnetic resonance spectroscopy detects pronounced changes in tumor cell high energy phosphate metabolism within 24 hr of (-)-gossypol treatment, manifest by 1.6- to greater than 50-fold differential reductions in the intracellular ratios of ATP/Pi, relative to (+)-gossypol-treated cell lines; the magnitude of these antimitochondrial effects correlates with the antiproliferative activity of (-)-gossypol. Northern blot RNA analyses suggest that treatment with a 5-10 microM dose of (-)-gossypol induces a transient increase in the expression of heat shock gene products, particularly hsp-70 transcripts. The mean 5-fold increase in (-)-gossypol-induced hsp-70 mRNA appears coincident with a comparable heat-stimulated increase in transcript levels, as compared with control or (+)-gossypol-treated cells. The enzyme-inhibiting properties of gossypol enantiomers were compared in cell-free assays measuring glutathione-S-transferase-alpha, -mu, and pi activities, calmodulin stimulation of cyclic nucleotide phosphodiesterase, and protein kinase C activity. Both enantiomers are near equivalent antagonists of calmodulin stimulation and protein kinase C activity, exceeding the potency of known inhibitors such as phenothiazines by as much as 50-fold. In contrast, (-)-gossypol is a 3-fold more potent inhibitor of glutathione-S-transferase-alpha and -pi isozyme activity, resulting in IC50 values of 1.6 and 7.0 microM, respectively, for these two isozymes.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract

We have previously shown that phenothiazines sensitize multidrug resistant (MDR) cells to chemotherapeutic drugs in a manner related to specific structural features, and have identified structurally related thioxanthenes with increased anti-MDR activity. We have now studied the structure-activity relationships of 16 thioxanthenes in the human breast cancer line MCF-7 AdrR. trans-Thioxanthene stereoisomers were 2- to 7-fold more potent than cis-thioxanthenes for antagonizing MDR. The most potent thioxanthenes possessed a halogenated tricyclic ring connected by a 3-carbon alkyl bridge to a piperazinyl or piperadinyl side group. The chemosensitizing effects of the lead compound, trans-flupenthixol, its stereoisomer cis-flupenthixol, its phenothiazine homologue fluphenazine, and the calcium channel blocker verapamil, were further studied in a series of sensitive and MDR cell lines. trans-Flupenthixol caused a greater reversal of cellular resistance to doxorubicin, vinblastine, vincristine, and colchicine in MCF-7 AdrR, KB-V1, and P388/DOX MDR cells than the other chemosensitizers. In particular, trans-flupenthixol was 2- to 3-fold more potent for reversing MDR than equimolar concentrations of verapamil. Furthermore, trans-flupenthixol fully reversed resistance to doxorubicin, vincristine, and colchicine in MDR MCF-7 and NIH 3T3 cells transfected with the mdr1 gene. None of these agents altered MDR in a non-P-glycoprotein expressing MCF-7 cell line selected with mitoxantrone, nor in any of the parental cell lines. The stereoselective antagonism of the flupenthixol isomers on several putative cellular targets was studied to explore the mechanism of their chemosensitizing activity. cis- and trans-flupenthixol were equally active inhibitors of protein kinase C and calmodulin. Both cis- and trans-flupenthixol were also potent inhibitors of [3H]azidopine binding to P-glycoprotein. The apparent lack of clinical toxicity of trans-flupenthixol makes it an attractive drug for possible use in the modulation of tumor resistance in vivo if appropriate tissue concentrations can be achieved.

Abstract

Triphenylethylene compounds, such as tamoxifen, have shown chemosensitizing activity independent of estrogen receptor status in doxorubicin-resistant cells. We examined the chemosensitizing activity of a new triphenylethylene, toremifene, and its major metabolites in a doxorubicin-resistant human breast cell line, MCF-7/DOX. In addition, we examined the chemosensitizing activity of unbound plasma toremifene and its metabolites isolated from patients treated with toremifene doses of 20 to 400 mg/d. MCF-7/DOX cells were exposed to ultrafiltrate plasma specimens in the absence and presence of doxorubicin. These latter studies were single-blinded. Toremifene and its major metabolites were capable of sensitizing multidrug-resistant cells to doxorubicin. The degree of chemosensitizing activity in vitro correlated with the plasma concentrations of toremifene and its metabolites (P less than .05). Plasma samples isolated from patients receiving high-dose toremifene (400 mg/d) had the greatest chemosensitizing activity. We present evidence that toremifene and its metabolites can sensitize resistant MCF-7/DOX cells to doxorubicin, that this effect is concentration-dependent, and that sensitizing activity can be detected at clinically achieved concentrations.

Abstract

Phenothiazines and structurally related compounds inhibit cellular proliferation and sensitize multidrug-resistant (MDR) cells to chemotherapeutic agents. To identify more potent pharmaceuticals, we studied the structure-activity relationships of 30 phenothiazines and related compounds on cellular proliferation and MDR in sensitive MCF-7 and resistant MCF-7/DOX human breast cancer cells. Substitutions on the phenothiazine ring that increased hydrophobicity increased antiproliferative and anti-MDR activities. For example, -Cl and -CF3 groups increased whereas -OH groups decreased potency. Modifying the length of the alkyl bridge and the type of amino side chain also influenced potency. Compounds with increased activity against cellular proliferation and MDR possessed a four-carbon bridge rather than a three- or two-carbon bridge and a piperazinyl amine rather than a noncyclic amino group. Compounds with tertiary amines were better anti-MDR agents than those with secondary or primary amines but were equipotent antiproliferative agents. The effects of these substituents were unrelated to hydrophobicity. The structure-activity relationships suggest that an ideal phenothiazine structure for reversing MDR has a hydrophobic nucleus with a -CF3 ring substitution at position 2, connected by a four-carbon alkyl bridge to a para-methyl-substituted piperazinyl amine. We subsequently studied related compounds having certain of these properties. Substitution of a carbon for a nitrogen at position 10 of the tricyclic ring, with a double bond to the side chain (thioxanthene), further increased activity against MDR. For example, (trans)-flupenthixol, the most potent of these compounds, increased the potency of doxorubicin against MDR cells by 15-fold, as compared with its stereoisomer (cis)-flupenthixol (5-fold) or its phenothiazine homolog fluphenazine (3-fold). (cis)- and (trans)-flupenthixol were equipotent antiproliferative agents. (trans)-flupenthixol was not accumulated more than (cis)-flupenthixol in MDR cells, implying that their stereospecific anti-MDR effects were not the result of selective differences in the access of the drugs to intracellular targets. Both drugs increased the accumulation of doxorubicin in MDR cells, but not in sensitive cells, suggesting that they modulate MDR by interacting with a uniquely overexpressed cellular target in these resistant cells. The apparent lack of clinical toxicity of (trans)-flupenthixol makes it an attractive drug for further investigation.